Reducing to compatible subset for licensing consistency

plugins/sampleplugin/sampleplugin.cpp

 /*
     SPDX-FileCopyrightText: 2009 Jean-Baptiste Mardelle <jb@kdenlive.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #include "sampleplugin.h"

plugins/sampleplugin/sampleplugin.h

 /*
     SPDX-FileCopyrightText: 2009 Jean-Baptiste Mardelle <jb@kdenlive.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #ifndef SAMPLEPLUGIN_H

renderer/kdenlive_render.cpp

 /*
     SPDX-FileCopyrightText: 2008 Jean-Baptiste Mardelle <jb@kdenlive.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #include "../src/lib/localeHandling.h"

renderer/renderjob.cpp

 /*
     SPDX-FileCopyrightText: 2007 Jean-Baptiste Mardelle <jb@kdenlive.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #include "renderjob.h"

renderer/renderjob.h

 /*
     SPDX-FileCopyrightText: 2007 Jean-Baptiste Mardelle <jb@kdenlive.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #ifndef RENDERJOB_H

src/render/renderserver.cpp

 /*
     SPDX-FileCopyrightText: 2021 Vincent Pinon <vpinon@kde.org>
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #include "renderserver.h"

src/render/renderserver.h

 /*
     SPDX-FileCopyrightText: 2021 Vincent Pinon <vpinon@kde.org>
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #ifndef RENDERSERVER_H

thumbnailer/mltpreview.cpp

 /*
     SPDX-FileCopyrightText: 2006-2008 Marco Gulino <marco@kmobiletools.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #include "mltpreview.h"

thumbnailer/mltpreview.h

@@ -3,7 +3,7 @@
     adapted for MLT video preview by Jean-Baptiste Mardelle
     SPDX-FileCopyrightText: Jean-Baptiste Mardelle <jb@kdenlive.org>
 
-    SPDX-License-Identifier: GPL-2.0-or-later
+    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 */
 
 #ifndef MLTPREVIEW_H