https://github.com/ChaosForge/doomrl
https://drl.chaosforge.org/
The code is under the GPL 2.0 license, while the original art is under the CC-BY-SA 4.0 license
So it is fully FOSS now, although some of the graphics are still questionable in regards to the DOOM IP. But if one was to fix that, it could be another cool FOSS game.