diff --git a/LICENSE.txt b/LICENSE.txt
index fc52e2a..0c9145b 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -1,5 +1,5 @@
 libstrophe XMPP client library
 Copyright (C) 2005-2009 Collecta, Inc.
 
-This program is dual licensed under the MIT and GPLv3 licenses.
+This program is dual licensed under the MIT or GPLv3 licenses.
 Please the files MIT-LICENSE.txt and GPL-LICENSE.txt for details.
diff --git a/README.markdown b/README.markdown
index 6c9da99..be79cf5 100644
--- a/README.markdown
+++ b/README.markdown
@@ -5,7 +5,7 @@ libstrophe is a lightweight XMPP client library written in C. It has
 minimal dependencies and is configurable for various environments. It
 runs well on Linux, Unix and Windows based platforms.
 
-libstrophe is dual licensed under MIT and GPLv3.
+libstrophe is dual licensed under MIT or GPLv3.
 
 Build Instructions
 ------------------
diff --git a/examples/active.c b/examples/active.c
index ced9789..937e2e3 100644
--- a/examples/active.c
+++ b/examples/active.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* active.c
 ** libstrophe XMPP client library -- basic usage example
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /* This example demonstrates basic handler functions by printing out
diff --git a/examples/basic.c b/examples/basic.c
index 69f73a1..fff4695 100644
--- a/examples/basic.c
+++ b/examples/basic.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* basic.c
 ** libstrophe XMPP client library -- basic usage example
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdio.h>
diff --git a/examples/bot.c b/examples/bot.c
index b8f5f94..976becd 100644
--- a/examples/bot.c
+++ b/examples/bot.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* bot.c
 ** libstrophe XMPP client library -- basic usage example
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /* simple bot example
diff --git a/examples/complex.c b/examples/complex.c
index 0546ede..bfcdfd6 100644
--- a/examples/complex.c
+++ b/examples/complex.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* complex.c
 ** libstrophe XMPP client library -- more complex usage example
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdio.h>
diff --git a/examples/component.c b/examples/component.c
index 1bf8b89..7e9d1a6 100644
--- a/examples/component.c
+++ b/examples/component.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* component.c
 ** libstrophe XMPP client library -- external component (XEP-0114) example
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /* This example demonstrates simple connection to a server
diff --git a/examples/perf.c b/examples/perf.c
index 3ed1a6f..5ce0934 100644
--- a/examples/perf.c
+++ b/examples/perf.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* perf.c
  * strophe XMPP client library -- performance measure
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/examples/register.c b/examples/register.c
index 0e3e289..e382c99 100644
--- a/examples/register.c
+++ b/examples/register.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* register.c
  * strophe XMPP client library -- In-band registration (XEP-0077)
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /*
diff --git a/examples/roster.c b/examples/roster.c
index bb89447..6779fc8 100644
--- a/examples/roster.c
+++ b/examples/roster.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* roster.c
 ** libstrophe XMPP client library -- handler example
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /* This example demonstrates basic handler functions by printing out
diff --git a/examples/vcard.c b/examples/vcard.c
index 777ab9c..1ed8cdf 100644
--- a/examples/vcard.c
+++ b/examples/vcard.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* vcard.c
  * strophe XMPP client library -- vCard example
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 #include <assert.h>
diff --git a/src/auth.c b/src/auth.c
index 30161c0..e354a66 100644
--- a/src/auth.c
+++ b/src/auth.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* auth.c
 ** strophe XMPP client library -- auth functions and handlers
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express or
 **  implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/common.h b/src/common.h
index e845f3e..478d7b9 100644
--- a/src/common.h
+++ b/src/common.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* common.h
 ** strophe XMPP client library -- internal common structures
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express or
 **  implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/conn.c b/src/conn.c
index 81926a7..cbedbad 100644
--- a/src/conn.c
+++ b/src/conn.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* conn.c
 ** strophe XMPP client library -- connection object functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/crypto.c b/src/crypto.c
index 7e6af39..779263f 100644
--- a/src/crypto.c
+++ b/src/crypto.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* crypto.c
  * strophe XMPP client library -- public interface for digests, encodings
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/src/ctx.c b/src/ctx.c
index 861788d..aa48f62 100644
--- a/src/ctx.c
+++ b/src/ctx.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* ctx.c
 ** strophe XMPP client library -- run-time context implementation
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/deprecated.c b/src/deprecated.c
index 46c5c03..8ec61ed 100644
--- a/src/deprecated.c
+++ b/src/deprecated.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* deprecated.c
 ** strophe XMPP client library -- File with deprecated API functions.
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/event.c b/src/event.c
index 7793392..82e5388 100644
--- a/src/event.c
+++ b/src/event.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* event.c
 ** strophe XMPP client library -- event loop and management
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/handler.c b/src/handler.c
index 43a2727..c6518d5 100644
--- a/src/handler.c
+++ b/src/handler.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* handler.c
 ** strophe XMPP client library -- event handler management
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/hash.c b/src/hash.c
index fd1039a..a32f319 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* hash.c
 ** strophe XMPP client library -- hash table implementation
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/hash.h b/src/hash.h
index 4e50fb3..fe29d3a 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* hash.h
 ** strophe XMPP client library -- hash table interface
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/jid.c b/src/jid.c
index 03f8387..ea4e3c9 100644
--- a/src/jid.c
+++ b/src/jid.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* jid.c
 ** strophe XMPP client library -- helper functions for parsing JIDs
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/ostypes.h b/src/ostypes.h
index aee5f5c..0ac5944 100644
--- a/src/ostypes.h
+++ b/src/ostypes.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* ostypes.h
 ** strophe XMPP client library -- type definitions for platforms
 **     without stdint.h
@@ -7,7 +8,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/parser.h b/src/parser.h
index dd735d9..ffebd9a 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* parser.h
 ** strophe XMPP client library -- parser structures and functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express or
 **  implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/parser_expat.c b/src/parser_expat.c
index 3d20766..c1d1d38 100644
--- a/src/parser_expat.c
+++ b/src/parser_expat.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* parser.c
 ** strophe XMPP client library -- xml parser handlers and utility functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/parser_libxml2.c b/src/parser_libxml2.c
index bc030c0..27f63de 100644
--- a/src/parser_libxml2.c
+++ b/src/parser_libxml2.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* parser.c
 ** strophe XMPP client library -- xml parser handlers and utility functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/rand.c b/src/rand.c
index c696944..bedfdaa 100644
--- a/src/rand.c
+++ b/src/rand.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* rand.c
  * strophe XMPP client library -- pseudo-random number generator
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/src/resolver.c b/src/resolver.c
index 53ca79f..becc438 100644
--- a/src/resolver.c
+++ b/src/resolver.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* resolver.c
  * strophe XMPP client library -- DNS resolver
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/src/resolver.h b/src/resolver.h
index f54cb09..7c7eb42 100644
--- a/src/resolver.h
+++ b/src/resolver.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* resolver.h
  * strophe XMPP client library -- DNS resolver
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/src/sasl.c b/src/sasl.c
index 66c3a81..74a6b43 100644
--- a/src/sasl.c
+++ b/src/sasl.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* sasl.c
 ** strophe XMPP client library -- SASL authentication helpers
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/sasl.h b/src/sasl.h
index 76ee799..bc5eb4e 100644
--- a/src/sasl.h
+++ b/src/sasl.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* sasl.h
 ** strophe XMPP client library -- SASL authentication helpers
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/scram.c b/src/scram.c
index 09f5ded..8938063 100644
--- a/src/scram.c
+++ b/src/scram.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* scram.c
  * strophe XMPP client library
  *
@@ -9,7 +10,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/src/scram.h b/src/scram.h
index b571396..59b79a2 100644
--- a/src/scram.h
+++ b/src/scram.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* scram.h
  * strophe XMPP client library -- SCRAM helper functions
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/src/sock.c b/src/sock.c
index d23ef51..c18fa14 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* sock.c
 ** strophe XMPP client library -- socket abstraction implementation
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/sock.h b/src/sock.h
index 0400422..9907f10 100644
--- a/src/sock.h
+++ b/src/sock.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* sock.h
 ** strophe XMPP client library -- socket abstraction header
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/stanza.c b/src/stanza.c
index ced649b..4a04a41 100644
--- a/src/stanza.c
+++ b/src/stanza.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* stanza.c
 ** strophe XMPP client library -- XMPP stanza object and utilities
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/tls.c b/src/tls.c
index afb6a52..9e7e18f 100644
--- a/src/tls.c
+++ b/src/tls.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* tls.c
 ** strophe XMPP client library -- generic TLS functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/tls.h b/src/tls.h
index 86e2bbc..9745572 100644
--- a/src/tls.h
+++ b/src/tls.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* tls.h
 ** strophe XMPP client library -- TLS abstraction header
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/tls_dummy.c b/src/tls_dummy.c
index 44df067..4b7b264 100644
--- a/src/tls_dummy.c
+++ b/src/tls_dummy.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* tls_dummy.c
 ** strophe XMPP client library -- TLS abstraction dummy impl.
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/tls_gnutls.c b/src/tls_gnutls.c
index bc6a08a..c78783a 100644
--- a/src/tls_gnutls.c
+++ b/src/tls_gnutls.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* tls.c
 ** strophe XMPP client library -- TLS abstraction header
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/tls_openssl.c b/src/tls_openssl.c
index 28e36be..8691197 100644
--- a/src/tls_openssl.c
+++ b/src/tls_openssl.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* tls_openssl.c
 ** strophe XMPP client library -- TLS abstraction openssl impl.
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/tls_schannel.c b/src/tls_schannel.c
index d48e59f..911a502 100644
--- a/src/tls_schannel.c
+++ b/src/tls_schannel.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* tls_schannel.c
 ** strophe XMPP client library -- TLS abstraction schannel impl.
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/util.c b/src/util.c
index efde98a..6faec99 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* util.c
 ** strophe XMPP client library -- various utility functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/util.h b/src/util.h
index f3d7750..4529086 100644
--- a/src/util.h
+++ b/src/util.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* util.h
 ** strophe XMPP client library -- various utility functions
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/src/uuid.c b/src/uuid.c
index 0951f9d..79ae0b1 100644
--- a/src/uuid.c
+++ b/src/uuid.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* uuid.c
  * strophe XMPP client library -- UUID generation
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /** @file
diff --git a/strophe.h b/strophe.h
index 7e9e7e7..b747252 100644
--- a/strophe.h
+++ b/strophe.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* strophe.h
 ** strophe XMPP client library C API
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express or
 **  implied.
 **
-**  This software is dual licensed under the MIT and GPLv3 licenses.
+**  This software is dual licensed under the MIT or GPLv3 licenses.
 */
 
 /** @file
diff --git a/tests/check_parser.c b/tests/check_parser.c
index 656d61e..cbc7679 100644
--- a/tests/check_parser.c
+++ b/tests/check_parser.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* check_parser.h
 ** strophe XMPP client library -- parser tests
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express or
 **  implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdlib.h>
diff --git a/tests/res_query_dump.c b/tests/res_query_dump.c
index 8fcff14..5780c80 100644
--- a/tests/res_query_dump.c
+++ b/tests/res_query_dump.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* res_query_dump.c
  * Simple program to dump res_query(3) response
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /* Linux and OSX:
diff --git a/tests/test.c b/tests/test.c
index 6b51c99..44e598e 100644
--- a/tests/test.c
+++ b/tests/test.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test.c
  * strophe XMPP client library -- common routines for tests
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 #include <assert.h>
diff --git a/tests/test.h b/tests/test.h
index 99c234b..9aa6188 100644
--- a/tests/test.h
+++ b/tests/test.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test.h
 ** libstrophe XMPP client library -- common routines for tests
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #ifndef __LIBSTROPHE_TEST_H__
diff --git a/tests/test_base64.c b/tests/test_base64.c
index a80cb9a..aa699b6 100644
--- a/tests/test_base64.c
+++ b/tests/test_base64.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_base64.c
 ** libstrophe XMPP client library -- test routines for the base64 codec
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <assert.h>
diff --git a/tests/test_ctx.c b/tests/test_ctx.c
index f173e0c..3e3d967 100644
--- a/tests/test_ctx.c
+++ b/tests/test_ctx.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_ctx.c
 ** libstrophe XMPP client library -- test routines for the library run-time
 *context
@@ -7,7 +8,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdio.h>
diff --git a/tests/test_hash.c b/tests/test_hash.c
index a5634aa..8be0873 100644
--- a/tests/test_hash.c
+++ b/tests/test_hash.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_hash.c
 ** libstrophe XMPP client library -- self-test for the hash-table implementation
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdlib.h>
diff --git a/tests/test_jid.c b/tests/test_jid.c
index ccd5fd2..9b8a5ad 100644
--- a/tests/test_jid.c
+++ b/tests/test_jid.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_jid.c
 ** libstrophe XMPP client library -- test routines for the jid utils
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdio.h>
diff --git a/tests/test_md5.c b/tests/test_md5.c
index 5d9c7fe..d86d8a9 100644
--- a/tests/test_md5.c
+++ b/tests/test_md5.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_md5.c
  * strophe XMPP client library -- test vectors for MD5
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /* gcc -o test_md5 -I./src tests/test_md5.c tests/test.c src/md5.c */
diff --git a/tests/test_rand.c b/tests/test_rand.c
index 183cea1..4b99f21 100644
--- a/tests/test_rand.c
+++ b/tests/test_rand.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* check_rand.c
  * strophe XMPP client library -- test vectors for Hash_DRBG
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /* gcc -o test_rand -I./src tests/test_rand.c tests/test.c src/sha1.c */
diff --git a/tests/test_resolver.c b/tests/test_resolver.c
index 0b8567c..e5699d2 100644
--- a/tests/test_resolver.c
+++ b/tests/test_resolver.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_resolver.c
  * strophe XMPP client library -- tests for resolver
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 #include <assert.h>
diff --git a/tests/test_sasl.c b/tests/test_sasl.c
index 6fc131a..adf52a9 100644
--- a/tests/test_sasl.c
+++ b/tests/test_sasl.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_sasl.c
 ** libstrophe XMPP client library -- test routines for the SASL implementation
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdio.h>
diff --git a/tests/test_scram.c b/tests/test_scram.c
index 7d92438..5d2984d 100644
--- a/tests/test_scram.c
+++ b/tests/test_scram.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_scram.c
  * strophe XMPP client library -- test vectors for SCRAM-SHA1
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /* gcc -o test_scram -I./src tests/test_scram.c tests/test.c src/sha1.c */
diff --git a/tests/test_send_queue.c b/tests/test_send_queue.c
index 83897f8..87d39cf 100644
--- a/tests/test_send_queue.c
+++ b/tests/test_send_queue.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_send_queue.c
 ** libstrophe XMPP client library -- test routines for the send queue
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <assert.h>
diff --git a/tests/test_sock.c b/tests/test_sock.c
index 3605083..4b5faa4 100644
--- a/tests/test_sock.c
+++ b/tests/test_sock.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_sock.c
 ** libstrophe XMPP client library -- test routines for the socket abstraction
 **
@@ -6,7 +7,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-** This program is dual licensed under the MIT and GPLv3 licenses.
+** This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <stdio.h>
diff --git a/tests/test_stanza.c b/tests/test_stanza.c
index 219f4fc..964532e 100644
--- a/tests/test_stanza.c
+++ b/tests/test_stanza.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_stanza.c
  * libstrophe XMPP client library -- test routines for stanza functions
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 /* gcc -o test_stanza -I./src tests/test_stanza.c -lstrophe */
diff --git a/tests/test_string.c b/tests/test_string.c
index 6d3f0d9..95c03b8 100644
--- a/tests/test_string.c
+++ b/tests/test_string.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_string.c
  * strophe XMPP client library -- tests for re-implemented string functions
  *
@@ -6,7 +7,7 @@
  *  This software is provided AS-IS with no warranty, either express
  *  or implied.
  *
- *  This program is dual licensed under the MIT and GPLv3 licenses.
+ *  This program is dual licensed under the MIT or GPLv3 licenses.
  */
 
 #include <assert.h>
diff --git a/tests/test_xmppaddr.c b/tests/test_xmppaddr.c
index 9f3ff3d..4b25535 100644
--- a/tests/test_xmppaddr.c
+++ b/tests/test_xmppaddr.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: MIT OR GPL-3.0-only */
 /* test_xmppaddr.c
 ** libstrophe XMPP client library -- test routines for the xmppaddr
 ** certificate API's
@@ -7,7 +8,7 @@
 **  This software is provided AS-IS with no warranty, either express
 **  or implied.
 **
-**  This program is dual licensed under the MIT and GPLv3 licenses.
+**  This program is dual licensed under the MIT or GPLv3 licenses.
 */
 
 #include <assert.h>