Aye, each website will be running on the same domain as its corresponding version of vB, but each website will have its own seperate domain. I should maybe mention that even though all sites will be running the same CMS, each site will have its own seperate members & vB databases, and member registration data will not be shared across sites.
Paul.
EDIT:
Ah!
Didn't expect to find this on vB.com, as I always see people getting pushed straight over here
http://www.vbulletin.com/forum/showthread.php?t=134605
^ This is exactly what I'm after, only this guy is far more eloquent than I