forums are created through accounts/login. So if you have a login name (free, btw), you can poke around in "your account" and create a forum.
So in the case of the main high fsh forum, the original owner has to give up her account, as the original account holder had to do for Blythe and I when we took over the pg bb as owners and moderators.
This (thunderdome) forum is simply a second forum created within that same account.
So if those forums' owners have other forums they moderate or simply don't want to give up their screen names, then we either get used to the trolls and annoying ads or create a new forum. (if you do searches, the very first high fsh bb is still around but dormant and has posts directing to the one that is active right now. ditto about the secondary IF bb, there is a new one that is active)
The one advantage to having a login is being able to edit your posts (in some forums). I can't tell you how often I've had to go back in to fix typos or delete some private info I regretted sharing
You can always propose starting a whole new high fsh bb, see how everybody feels. Depending on traffic, it costs about 35-40$ every 6mos to get rid of ads that pop up, as owner/moderator you can delete the posted ads and trolls. BUT I think that the main high fsh bb gets more traffic than the pg bb so it might cost more than 35$/6mos and as long as you get donations...
Look at the links on the right side of the main high fsh, you'll find the original high fsh bbs.