2 forums on the same server. can I share user list?

[Faustus]

Meaning can I make it so the members of one forum automatically have access to the other?

[Jade Elizabeth]

Assuming they use the same database you can use this turorial
http://www.simplemachines.org/community/index.php?topic=16190.0

I use it and its awesome, I recommend the membergroups and members tables for what you want, and perhaps the permissions too