Infinite Rain has written
Correct me if I'm wrong, but isn't it only illegal if you use title/resources in commercial purposes? CS2D is 100% free, so why is it still a problem to upload to steam?
This is a myth. Valve could actually just sue you if you upload their logo on any website. It doesnt matter if you get money from it or not. It's illegal.
Well but ofc they wont sue you if you do this just because they don't really care. But uploading a game with that much copyrighted stuff from Valve on Steam would be... well it would be DC's suicide.
So if DC wants to put CS2D on Steam he has to remove every copyrighted stuff. This does ofc also mean that he would have to rename the game.