Use PunBB registration for comments

I have a site with several php scripts, including Punbb and an RSVP script that use the same members table in MySQL.

I’ve never bothered integrating the WordPress’ users table. I want to keep the blog somewhat seperate from the public forum.

But it would be nice if people can comment in WP under their Punbb login. Is there a way to do that? Where should I start?

And please don’t tell me I should use WP as my main registration script. ??