Valve has released the complete client and server code for Team Fortress 2 (TF2) as part of its Source engine Software Development Kit (SDK), allowing developers to create game modifications. The SDK enables fans to "change, extend or rewrite" the TF2 experience, but all modifications must be non-commercial and offered free of charge. TF2 mods can be published on the Steam Store as new games. Valve emphasizes the importance of respecting community contributions and encourages mod creators to integrate community-driven content with the new modifications while honoring the work of Workshop contributors.