Return to Castle Wolfenstein - licensed under the GPL
ID Software has published the
source codes of the classic 3D shooter Return to Castle Wolfenstein ( RTCW-SP-GPL.zip
), as well as multiplayer ( RTCW-MP-GPL.zip
) and Wolfenstein add-ons - Enemy Territory ( ET-GPL.zip
). All this is published under the GPL license.
On the ftp server, the source is not only for Windows, but also for Unix and MacOSX. They include only the game engine, but not the graphics.
The same ftp also contains the sources of other games, including Quake 1, Quake 2 and Doom.