Still a lot of room for improvements but I think some folks might get some enjoyment out of it so far and potentially have some feedback to give. Check out the assets/docs/darkmatter-todo to get an idea of how I'm looking to develop the source port.
Edited 32 seconds after the original posting.
If you want an existing example, there's FTEQW, which started as a quakeworld source port to add some modern things (as in loading TGAs, oggs, skyboxes), then support for other games were gradually creeped in ("netquake", Hexen II, Quake2, Quake3) with varyingly "off" results.
Edited 35.43 minutes after the original posting.
Yeah FTE has some similar features to what we set out to do.