Question about Multiple Sub-Forums

[Cystomatic]

Hello vBulletin community.

I have a question. If I have a website, lets say: forum.com and I would make different subforums such as subforum1.forum.com, subforum2.forum.com etc., would I have to buy a different vBulletin license for each subforum, or can I just use the vBulletin license for all the subforums?

Thanks a lot.