There's only one caveat, you have to release your game on Steam along with wherever else you launch it. http://www.rockpapershotgun.com/2015/03/04/source-2-is-actually-free-like-for-free/ Valve’s sudden entry into the engine race, with an official announcement of Source 2, seems to have put them right up front alongside frenzied rivals Unity and Unreal. (Poor old Crytek, eh?) Meeting with studio founder Erik Johnson today, I learned that when they say Source 2 is “free”, they mean it. Unlike Unity’s (much lowered) subscription rates (for larger teams), and Epic’s revenue cut of successful projects, Valve won’t be asking for any money at all. Well, sort of… They just require that the game be launched on Steam, along with anywhere else you might want to sell it.