Most of those ports are being done by one lone developer named Ryan C. Gordon who runs icculus.org Here's a talk he did about porting games to Linux with SDL 2.0 during a Steam Dev Days event: https://www.youtube.com/watch?v=MeMPCSqQ-34 One interesting thing to note is that most of those Linux ports can only be purchased through a Humble Bundle. (Playdead's Limbo is a case in point.) It goes without saying that the grand majority of those ports would have never happened if it weren't for Humble Bundle in the first place.