See also:
Quake Engines & Source Ports: A Beginners Guide - https://www.slipseer.com/index.php?threads/quake-engines-sou...
LibreQuake - free and open-source Quake remake with art under the BSD license - https://github.com/lavenderdotpet/LibreQuake
Chocolate Doom - https://github.com/chocolate-doom/chocolate-doom