This announcement came in today:
The Clemson Linux User Group is sponsoring a project to create an open source mod for Unreal Tournament 2004. The gameplay for this mod will focus on racing and combat with the flying vehicles in the game, especially the hovering Manta. The game and the code are not available yet, we plan to kickstart development with a collaborative programming event in Clemson University’s Hardin Hall auditorium on November 6 called the Clemson Open Game Hack. Also, one of our members has set up a UT2K4 Linux SDK, a collection of scripts to make development on Linux easier. You can read about it on the Beyond Unreal Wiki Entry.