Seamless integration between WordPress and BBpress

I have a WordPress site at domain.com and a BBPress install at domain.com/subfolder
the wp site has a menu item that goes to the forums, and I’d like the header to be the same between the two, so that they can navigate back to the main site.
how can I do that?

thanks

As far as I know there is no easy way to do that. The only way I’ve seen so far is customizing WP and BBPress themes to match. For example http://themehybrid.com/ (WordPress) and http://themehybrid.com/support/ (BBPress).