BuddyPress.org

Howdy. Your bbpress install is probably in a subdirectory under your document root. Looks like in /groupforum. In that subdir you put your bbpress .htaccess file that bbpress recommends for you. In your document root goes your wpmu .htaccess file that wpmu generates for you. bbpress doesn’t generate one. You have to copy/paste it to an editor and then put it in your bbpress install directory.