Valve releases Team Fortress 2 SDK allowing creators to make games

Two years after radio silence, Valve has finally introduced a major change for Team Fortress 2 by releasing the Source SDK, including all of TF2's client and server game code. Modders now have much-needed freedom to improve the game or create entirely new games based on TF2. These games can then be released as standalone titles, similar to Garry's Mod.