Well, it may be an attempt to get a script done for him, but usually when people do that they say it must do "this", "this", and "this". He has left it pretty vague and at least is offering some form of compensation (for the winner, anyway) for making the script.
Also, if you don't wish to enter, then that's no problem. If you do enter, you can also make a disclaimer stating that it cannot be used in a game. There's nothing here stating that your script MUST be usable in a commercial (or otherwise) product, so I'm assuming you retain the rights to whatever you enter.
The one and only,