Wolfenstein 3D
Although id Software did not develop another "Wolfenstein" game, as their development focus shifted to "Doom" shortly after release, and has never returned to the series, multiple "Wolfenstein" titles have been produced by other companies, sometimes using game engines developed by id. The first of these newer "Wolfenstein" games was "Return to Castle Wolfenstein" in 2001, a reboot of the series, and the latest is the 2017 "".
Wolfenstein: Enemy Territory
The game uses a modified "Return to Castle Wolfenstein" engine, itself being a heavily modified id Tech 3 engine, which has been open source since 2005. As of the first day of the August 2010 QuakeCon, the entire source code was released under the GNU General Public License v3.