This uses Threads Groups for access. So if your stuff can authenticate to threads - it would work.
Basically if group #5 is the paid group - when a user pays, it puts them into group #5 within threads. From there, you can restrict them from viewing forums, using features (with some hacking) or photopost (again using the threads groups).
So it's not really like htaccess, and there's no separate user database. It's all tied to threads.
