Valve has confirmed that its Source software development kit will be made available for free to anyone that wishes to use it. The news isn't entirely surprising considering the current requirements of obtaining the Source SDK. Currently, the SDK is available to users that own at least one Source-based title, a redundant stipulation considering Team Fortress 2's new free to play changeover.
The move was confirmed earlier today by Rock, Paper, Shotgun, after original word came from a Reddit thread detailing the change. Asking Valve's Robin Walker if purchasing an item in the Team Fortress 2 "Mann Co. Store" would give users access to the Source SDK, Walker replied: "Yep. That said, your email has triggered a process here that made us re-examine that, and we’re going to just go ahead and make the Source SDK freely available. Thanks for making us better!"
Walker tells RPS that Valve is still in the process of making the change, which is a complicated process due to the multiple versions of the SDK. The "gist," he says, is that the Source SDK will be made freely available to all.
If you're interested in exploring your creativity with the Source SDK and don't know where to start, make sure to check out the engine's official documentation.
An official announcement and estimated time for the switch has yet to be revealed.