Make forums available for Supporters only

I like how Edublogs makes "Forums" available only to supporters. I'm wondering how to set up forums on my WPMU install to work with the supporter plugin?

Question 1. I assume you recommend using Andrew's Forums plugin over bbPress for this?

Question 2. I tried installing the forums plugin, but I'm not sure how to make it only accessible to supporters. Any clues?

Thanks so much.