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 the…
"We're already preparing for the porting efforts and a potential Steam release now that we've been legally enabled to pursue ...
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 of other improvements." ...