BuddyPress.org

The default view for the member directory is “active members”. This will only show users who have logged in since you activated BuddyPress, and are therefore considered active (last_activity meta is present). If you change the ordering to something else, the members will show.

Technically this comes down to if a user’s “last_activity” record is present in wp_usermeta. I suppose you could pre-prime the last_activity record by something like this: http://buddypress.pastebin.com/USrLFAFH It’s not tested, but I think you could put it in your functions.php. Remember to remove it after one execution, however(!)

BuddyPress doesn’t use bb_users at all, only wp_users.

You have a standalone installation of bbPress which is where your users database is (because you mentioned bb_users, I expect)? Can we just clarify that you’ve installed WordPress, and activated BuddyPress?

Have you integrated your standalone bbPress install at all? If so, how? Via the “Use an existing bbPress installation” button in the BuddyPress Forums Setup page?

Hmm it depends how you want your site to work. At the moment, it’s a one group to forum mapping. That means, for each forum (or sub-forum), you’re going to need a group.

How many (sub)forums on your existing site? If you have more forums than you want BuddyPress Groups created, we need to do some more work to configure your setup to integrate your WordPress into an external bbPress installation. This is not technically easy, and would involve you creating a separate theme for the bbPress site itself.
A benefit of this approach is that you have full access to a traditional forum look-and-feel (bbPress’).

If, however, you’re happy with how the one forum to group mapping works with BuddyPress, you’ve already done the installation (i.e. clicked the button that said “use an existing bbPress installation”). What you’ll need to do next is move your users from the bb_users table into wp_users (and usermeta too if you want, but be careful and consider if you need to do that), create some groups and then edit their database entries to point to the existing bbPress tables.

Hopefully someone else will chime in, but the only thing you may lose by not importing the bb_usermeta would be any customisation a user has done to their “display name” or “nice name”; it’d default back to that person’s username. They’d have to just type their preferred display name back in to WordPress or bbPress, so nothing tricky. So, I don’t think you need to.. probably.

I get the feeling you’re aware of this, but I’d suggest having a test-run of this to find out how well it works (or doesn’t) before doing it on your live database. Also, check that bb_usermeta and wp_usermeta have the same columns, you may need to massage the import a bit.

Once you get the users into WordPress, and you can log in as one of them, we can see about associating existing bbPress forum posts with a particular BuddyPress Group’s forum. I’ve not done that myself so hopefully someone who has can guide.

Re: moving standalone bbPress forums to BuddyPress group forums, I would recommend reading an excellent post by BP moderator, Boone Gorges:

Upgrading from BuddyPress 1.0 to 1.1