What they do is contact your host & have them shut you down, if they don't then your host get's into legal issues & so will you. I imagine that if you're found to be "guilty" multiple times then vb might chase after you with a lawsuit, so if that's what you want then go for it.
There really is no point... if you want to use vBulletin, pay for it. If you want something free that's pretty good (and in some ways better than vBulletin), use MyBB.
thanks bro for answering my stupid question i am not going to involove in any illegal activity but also want some knowledge about it and i am really very happy that the king of vb forum sites answer my question. one more question i want to ask that which one is the best free forum site my bb or any other.