The $10,000 first prize sounds very nice, but do be very sure to read and consider the rules very carefully, especially rule #8:
Right to Use Your Work and Information About You: By submitting an Entry, you: ...http://www.addicting...m/contest/rules.html
(b) automatically grant to Atom Entertainment, Inc. a non-exclusive, world-wide, irrevocable license to use, reproduce, create derivative works from, modify, publish, edit, translate, distribute and display the Entry, which shall last only through the end date of the promotion and continue for 90 days thereafter, after which all such license rights shall terminate, and any right that remain shall revert to Entrant;
(c) agree that upon selection as a winner of any prize, you agree that your Entry shall legally be considered a "work made for hire," with all rights therein, including, without limitation, the exclusive copyright, transferred to and being the property of Atom Entertainment, Inc.; (d) agree that upon selection as a winner of any prize, in the event your Entry is considered not to be a "work made for hire," you irrevocably assign to Atom Entertainment, Inc., all right, title, and interest in and to your Entry (including, without limitation, the copyright) in any and all media whether now known or hereafter devised, in perpetuity, anywhere in the world, with the right to make any and all uses thereof, including, without limitation, for purposes of advertising or trade; and (e) agree that upon selection as a winner of any prize, you grant to Atom Entertainment, Inc. the right to sell and otherwise distribute your Game submission on any of its websites without any compensation.
In other words, as i read it: even if you win a $500 honorable mention prize, you have effectively sold them the sole rights to your game, which they can then sell, distribute, etc., soley for their profit.