In Bonus Settings I see the following explanation:
Sites that use a combination of BBPress and BuddyPress need all users to be subscribed to the blog on which BBPress is installed. The following section lets you do that. Note that you may add people to a comma-delimited list of blogs, but they will have the same role on each blog.
And there is a checkbox to "add user to other blog(s).
Not clear to me what this does... Is it that
IF I have turned on MU for WP3, so I have a networks of sites,
AND I install BBPress on my main site,
AND I enable somehow the subsites to have their own Forums but running of the same central database,
THEN I need to check the checkbox so the new users from the subsite becomes a user of the main site and thus enables them to post in the subsite BBPress?
Or am I way off??