Fix wording of licensing terms

It has been pointed out that the wording of the license of this library is
not entirely clear.

The term "dual licensing" usually refers to a licence choice of two
licenses "LICENSE1 _or_ LICENSE2.
Instead the license of this library claimed "LICENSE1 _and_ LICENSE2".

After an internal discussion with @metajack and @pasis it was made clear
that the initial idea was to dual license the library in the usual way.

This was also made clear by jack on the ML in the past [0].
As of jack, these licensing terms originated from jquery, which also used
the 'and' version in the past and has since been corrected [1].

This patch changes the license terms to 'MIT or GPLv3' and also adds SPDX
headers [2].

[0] https://groups.google.com/g/libstrophe/c/JkFgr601JQc
[1] https://stackoverflow.com/q/2758409
[2] https://spdx.org

Signed-off-by: Steffen Jaeckel <jaeckel-floss@eyet-services.de>

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>

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:

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>

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__

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>

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>

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>

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>

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 */

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 */

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>

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>

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 */

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>

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>

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 */

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>

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>