Regarding Rights and Privileges

At the time of winning (either at the time of notification or publication of results, whichever comes first), the winner is considered to have agreed to give KADOKAWA exclusive rights on the use of the winning content (including all related novelizations, electronic novelizations, comic adaptations, animation, motion pictures, games, merchandise, digital goods, translations, as well as other adaptations, reproductions, and uses, including granting said uses to third parties).

The winner also cannot use the submitted work for commercial reasons for either themselves or other third parties outside of our company without prior written consent.

Also check this:

I don't think it's a scam at all. There is a game jam with similar condition for winner. It called IGMC 2018 host by Degica. The jam is done well. I don't see any problem happened there to the winner.

While they're not the same company but both associated with Maker Series. KADOKAWA is the company that developed both RPG Maker MV and Pixel Game Maker MV. There is no reason to not trust them.

If you worry that much , you don't have to submit the game that you think it gonna make you a billion dollar! (if it ever make that much lol) You can come with new fresh idea whatever you want.

This is the game jam. Just have fun! Let's make the game.