I had a huge amount of fun back in those days messing with QuakeWorld and Quake2, learned a ton of stuff.

One project was embedding a Python2 interpeter in QuakeWorld, along with a QuakeC->Python translator. The translator and the resulting Deathmatch and CTF games are here: https://github.com/barryp/qwpython

The other was embedding a JavaVM in Quake2, and instead of trying to translate the C game logic, we recreated the whole thing from scratch in an object-oriented Java fashion: https://github.com/barryp/q2java

Thanks to Carmack for opening up those old engines, that was a real education.