I would of asked this on VB's own site, but it's down at the mo. I know you can buy a VB licence for one domain name, but could you have several forums hosted on sub folders of the same domain name you hold the licence for?
You can have your forum on a subdomain, or within a folder or whatever, but it's still just ONE instance of vBulletin per license. So one license allows you to have yourforum.yourdomain.com or yourforum.com or yourdomain.com/yourforum/ but not all three. EDIT: You can actually have all three point to your main forum, so long as there is only one instance of vB running per paid license. What you can not have is three separate instances of vB running while just buying one license.
Yes I think you are right. I'll ask over at VB, just in case, but looking at the licence agreement, it looks as if it just one forum per domain.
Yes it is one instance per one domain. I have been using vBulletin and had a similar question like this long ago. You can however use their bulk purchase to get multiple licenses so you can have other instances of vBulletin running.
I sometimes forget that simpler can be better. Thanks for doing in 5 words what took me 5 lines to say