Warsow was greenlit. As far as I know, this is the first open-source game on Steam. I was under the impression that the terms of the GPL (idtech2 engine) precluded integration with the Steam libraries, but they must have found a way around it.
I think (without looking deeper into it) that as long as you don't use the steamworks features (which many games don't do), distribution via Steam doesn't need much deeper integration which could conflict with the GPL.
Hopefully this will revive Warsow a bit, since it has been somewhat dormant lately.