Integrating phpca into a blog?

Has anybody ever managed to integrate a rather large program like PHPCA (classified ads, http://www.phpca.net) into a page in a blog, so that it shows up inline within the theme? The RS-Discuss forum is a great example of what I’m talking about – a discussion forum that looks like PHP-BB (sorta), but is totally inline within the theme, even going so far as to share user registration data with WP. Has anybody attempted this with a classified ads program?