Member account links across separate forums?

[blankoboy]

I am wondering if it is possble to have a VB forum at domain 1.com and 2.com and have the memberships be shared across both sites.

So, if a user registered at 1.com he/she could sign onto 2.com with their same membership without having to re-register. Can two forums share them same user db?

If not, is it possible to have a subsection (categories/sub-categories) of a forum be the main forum for another URL?

1.com - main forum and sub forums (all 2.com categories also here).
2.com - only a set of specific sub forums from 1.com

I hope I'm making sense here? Thanks.