Quakemaster Ajay (or old git as he likes to be known on the forums ) has updated his site with info about his QuakeDC mod, which unfortunatly he has been having problems with.
Be sure to check out Dreamcast Quake for future progress reports.
UPDATE: For those of you that have been e-mailing me about it, yes, I know that Quake 2’s source has been released. You can read a forum topic about it here & there’s also one in the QuakeDev forum.