Thanks for bringing this to my attention Cristián.1. I cannot view my forum through my Wordpress site - it seems to be a standalone bbPress site (I hoped to see it working through the Wordpress Thesis theme).
You could certainly re-theme bbPress to match your main site, but you are correct; bbPress is a separate software installation, it is not part of WordPress in any way. So, it is possible to integrate your bbPress user database with WordPress and s2Member, but the software will remain stand-alone in all cases.
2. When I try to login to the forum as the KEYMASTER (username=admin), it does not recognise the user any longer (it was working before I installed the BBPRESS integration plugin).
Yea, I've seen this reported before, and it seems to be related to a mix-up in the
bbPress -> WordPress integration on some installations. Although I'm not sure exactly what causes this, it seems to happen when the same username is used for both WordPress and bbPress administrative/keymaster access. The easiest way that I've found to resolve this, is to access your MySQL database with a tool like phpMyAdmin.
Go to phpMyAdmin, and take a look at your `wp_usermeta` table.
Add a new entry with the following data fields.
user_id = the ID of your keymaster account.
meta_key = bb_capabilities
meta_value = a:1:{s:9:"keymaster";b:1;}