As Cheebo pointed out, that's just an imdb page. The studio didn't put that up, a fan did.
I think it's somewhere back in that thread (because I was confused as hell about this too) where someone pointed out to me where and how I'd gotten confused about there being a greenlight.
But basically, Fox has not given this guy a budget to make a movie yet. They're going to let him develop his ideas, and then they're going to see if those ideas are strong enough to give him a budget. Only when the checkbook actually comes out is the film "greenlit"
So far as anyone knows, that has not happened yet. I don't know if Blomkamp said differently on his instagram in the meantime though. I thought he'd simply said he and Fox are going to gonna start working on it - but you can work on a film for a studio and not have the film greenlit.