[Boone Gorges]

Having existing users on the forum definitely makes it more complicated. But in the end, any integration plugin is going to have a username/user_id cross-reference, so you’d just have to write a script that does the initial setup with your existing users.

Your other option is to try to modify BP’s internal bbPress to do what you want it to do. The biggest hangup will be subcategories, which you might be able to fake with something like forum tags. But this path might be easier, given that you wouldn’t have to deal with cross-platform issues.