Valve adds "all the Team Fortress 2 client and server game code" to its Source mod tools, letting modders "build completely new games based on TF2" and publish them on Steam
"We're already preparing for the porting efforts and a potential Steam release now that we've been legally enabled to pursue that," according to one mod dev ...
Valve releases 'Team Fortress 2 SDK,' enabling creators to 'build completely new games based on TF2'
Valve has also released major updates to all Source-engine multiplayer games adding 64-bit support, scalable HUDS, "and a lot ...