i want to follow the easiest way for login integration with opensource forum script. I think that they set a particular flag or batch for remembering logged in user with session(example $_SESSION['valid_user']). suppose phpbb forum checks logged in user by $_SESSION['valid_user'] and users are now at Drupal site. We need drupal site users will automatically get access to phpbb forum. but i am thinking to modify current login script that will also set a $_SESSION['valid_user'] i'll also modify phpbb login code because wherever phpbb redirects for login page of phpbb, it will redirect to Drupal login. finally i'll remove registration part from phpbb. Do you think that my logic is still missing any part of this job? or there is still more easy way to do it.
Try to convert the login from your forum to drupal and then replace the current login to forward to the drupal login page.. So it seems you are thinking right!