It's been available in piracy form for quite a while now, however i think this guy just simply got his preorder early.
I think it's rubbish atm but then i've only played it for half an hour. Enemies respawn when you leave areas, so you'll clear a checkpoint but then when you pass through it again later you'll be met with gunfire. Also my car got stuck on a wooden picket fence and refused to move, the result of this was me having to run for a good 5 mins just to get to another car. It's nothing like Farcry 1, but this is unsurprising considering its developed by completely different people, is set in africa and doesn't have the main character from the original in it.
[EDIT] Oh, and as far as i can tell, there aren't any mutants in this one either