I am the owner/author of RokBridge, a phpBB3 bridge for Joomla. We try to keep our bridge as clean as possible, but there are a few issues that force us to patch minor things in phpBB3. One of these is the build_url() function in the functions.php file. This function returns:

return $phpbb_root_path . str_replace('&', '&', $redirect);

I was wandering if this could not just be:

return str_replace('&', '&', $redirect);

This removes the hardcoding, and still seems to work fine. This way it allows the bridge to function properly.