Activision and Raven Software game studios have open sourced a couple of their games so that people can play as well learn from the code. The gaming companies have released the source code of Star Wars Jedi Knight: Jedi Academy and Jedi Outcast through SourceForge."

http://games.slashdot.org/story/13/0...ames-under-gpl

Could these be portable to Dreamcast or other hombrew consoles ?