The Linux version of Steam, currently in beta, is going to be joined by the addition of Team Fortress 2, accompanying Left 4 Dead 2 - showing the ongoing effort at Valve to port their games over to the platform.

Steam's Content Record Description on Linux references a 'Team Fortress 2 Beta' as well as a link to this faux manual.

Team Fortress 2 makes sense as Valve's next effort on Linux, as it represents a test of multiplayer gaming, as well as persistent item servers. Left 4 Dead 2 performed far faster on Linux than it did on Windows, so it looks likely that Team Fortress 2 will see the same results.