If you put an MD5 in the database and use it to login to phpbb, it works. If you try to pass it to some other application that is expecting and MD5, it won't work, because it gets salted.
So, what are you trying to do?
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The password doesn't just get salted. It does 2048 iterations of md5($hash . $password) after md5($salt . $password).
If you can be a bit more specific on what it needs to do we can possibly figure out a way to get it working. Do you need it setup so the game engine can check your database for the users or just to have it register users on your board after they register via the game?