Login to your customers area, then follow the Compiler
tool. You will be able to check this Premium add-on and compile it to the core right away. Then look how it's being installed in bb_plugins.php, you could also compile the other add-ons this way.
The basic thing needs to be done with this function, is that it could not be duplicated. One function combines all the add-on codes for it. Possibly you have duplicated this function, that's why you are getting the fatal error (blank page comes for it if error messages are supressed in your PHP configuration).