It's not GTA 5, but hey...
http://store.steampowered.com/app/206420/
This also includes "Gat out of Hell", but..while I have not played, it is obviously a kind of cash grab as should have been DLC for 4, but I digress. At least it's like..5 bucks right now.
Does this mean I will stop playing Fallout 4? Probably Not. But this is cool, it is not just another "might as well make a Linux, we made the Mac", Aspyr project, which has been kind of slow lately, though KOTOR 2 is also playable on Linux as well now, but this is something I am sure most could accomplish by accident with WINE, so..