DualShockers

Valve has released the Team Fortress 2 SDK, which means we can expect a load of new content from the modding community.

Valve releases TF2 SDK to the public for modders, allowing changes ranging from tweaks to complete conversions. Modders can create TF2 mods for non-commercial use only, must be free, and not profit ...
TechSpot

Valve releases full Team Fortress 2 SDK, modders gain control over the game's code

Why it matters: Team Fortress 2 launched 17 years ago but still receives significant updates, and its player base is as healthy as ever. The latest patch fully unlocks the game's SDK, releasing ...
Engadget

Valve hands the Team Fortress 2 source code to modders

Valve is handing Team Fortress 2 modders the keys to the kingdom, as long as they don't try to make any money from it. The company has added the client and server game code to the Source software ...
MMORPG

Valve Drops Full Team Fortress 2 SDK, Allowing Any Modder or Dev To Make (Free) Derivative Work

Team Fortress 2 has had its biggest update yet… by making anyone able to update it. Valve officially dropped the SDK (software development kit) for the long-beloved multiplayer shooter game for free ...