Hi,
I've been looking for a user integration like this for Wordpress and punBB. 
I tried to do this but I can't seem to get it to work.
I have installed punBB on http://www.mmo-gamer.com/community/ and WP is installed in the root: http://www.mmo-gamer.com/
I put the plugin file (not the folder) in the plugins folder after updating it, changing ../punbb to ../community and then activated it. But it doesn't seem to work. I cannot login to punBB with current Wordpress users.
I haven't done the redirection steps with the other files yet; I wanted to db integration to work before I started with that.
What am I doing wrong?