http://ru1337.com/darsana/
The Engine...
http://icculus.org/twilight/darkplaces/
I was chatting to Chris (the developer) and Aazumak (A Modeller) who are creating Darsana, they are looking for interested people than can help out, mappers in particular, so if any of you guys have some free time give Chris a shout on his website.
You can map with GTK or Radiant, Chris will fill you in on the details
The Engine spec sounds pretty good too




