Is there a time period before Degica relinquishes the rights to First Publishing if they don't use it? Otherwise, it seems a bit unfair to tie up the game by preventing the winners from publishing (since if Degica decides not to publish, then the game basically can never be published under the rules of First Publishing Rights).
Creators retain all rights to their respective works. The contest runners (Degica) reserve the right to promote the game on the appropriate websites, blogs, social media, etc. as outlined in the prize packages.
Degica reserves first publishing rights for games that win Degica’s Choice, People’s Choice, and/or YouTuber’s Choice.
Those two lines actually seem to contradict each other to a certain extent. Creators retain all rights to their respective works, but Degica reserves the right to promote entries and the right to first publishing for winners. So the right to promote entries can be non-exclusive, but first publishing rights are generally exclusive.