Well, if it is a good null, how are they going to find that your board is not a purchased copy. There a few ways they look for it being nulled and a good nulled copy can stop them. I know many many sites that have a nulled vb board on them and they have never been down.
Well vbulletin licenses are by domain. So if someone reported the sites they would be hearing from someone then.
I think he's talking about the "homecalling" feature that vB users talk about. Jelsoft will know, but not many ordinary users will be able to distinguish a legitimate vB running board to one that is nulled. By the way, phpBB3 kicks some major vBulletin butt, and is a solution you could go if you can't find a "nulled" allowing host. I'm thinking of liquidating a few of my licenses..