After Disney shut down LucasArts recently, Raven Software open sourced Star Wars Jedi Knight II: Jedi Outcast and Jedi Academy.
The source code was made available on SourceForge, however it was pulled down after few days as some proprietary stuff was included in the public repository.
Raven Software may upload the source code again after sorting out legal issues. However, community is already working on improving the game.
One such project is OpenJK, which aims to improve Jedi Academy. All proprietary parts has been stripped off from this repository.
In another effort, Jochen Leopold is porting Jedi Outcast to Linux. He posted a screenshot of the game running on Ubuntu.