Update license in all READMEs (forgot to do that)

mods/fire/README.txt

@@ -6,11 +6,11 @@ License of source code:
 Copyright (C) 2012 Perttu Ahola (celeron55) <celeron55@gmail.com>
 
 This program is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2 of the License, or
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
 (at your option) any later version.
 
-http://www.gnu.org/licenses/gpl-2.0.html
+http://www.gnu.org/licenses/lgpl-2.1.html
 
 License of media (textures and sounds)
 --------------------------------------