I mean, it DID work with Source/hammer. They’re two parts of the same package. And a good number of games used a licensed Source engine.

VtmB is an early but jank example. Apex Legends is a modern, successful one. https://developer.valvesoftware.com/wiki/List_of_third-party_Source_games

And also because they installed Fedora for the PC they were building for Torvalds in this video, yes.