If you are running Joomla 3.x and want to not only run phpbb3, but embed it into your site, then get this extension. Install Joomla, Install phpbb3, then install the bridge. Be sure to follow the included guide. It installed flawlessly for me. I had some confussion with multiple logins where it shows if you have the Who's on module active. I had some minor issue with setting the cookie settings in phpbb3 but Alterbrains has amazing support and will patiently work with you on getting it set up.
Thank you AlterBrains!