https://openarena.ws/svn/source/assets/COPYING

It’s definitely done, apparently new development is still happening, but there hadn’t been a new release for a long time.

Assets are licenced under the same licence as the engine, GPL2.

Licence for game assets: https://github.com/OpenArena/gamecode/blob/main/LICENSE

How about open arena? http://www.openarena.ws/

Kubernetes is probably overkill, docker compose will work fine for most home labs. But I agree with your point, declarative infrastructure makes life so much easier, even for home labs.