So I'm about to submit a game to a competition, but as I looked through the rules a chunk grabbed my attention:

All Entries become the sole and exclusive property of Sponsor and will not be acknowledged 
or returned. Sponsor shall own all right, title and interest in and to each Entry, including 
without limitation all results and proceeds thereof and all elements or constituent parts of 
Entry (including without limitation the Mobile App, the Design Documents, the Video Trailer, 
the Playable and all illustrations, logos, mechanicals, renderings, characters, graphics, 
designs, layouts or other material therein) and all copyrights and renewals and extensions of 
copyrights therein and thereto.  Without limitation of the foregoing, each Eligible Entrant
shall and hereby does absolutely and irrevocably assign and transfer all of his or her right, 
title and interest in his or her Entry to Sponsor, and Sponsor shall have the right and may 
authorize others to use, copy, sublicense, transmit, modify, manipulate, publish, delete,
reproduce, perform, distribute,  display and otherwise exploit the Entry (and to create and 
exploit derivative works thereof) in any manner, including without limitation to embody the 
Entry, in whole or in part, in apps and other works of any kind or nature created, developed, 
published or distributed by Sponsor and to and register as a trademark in any country in 
Sponsor’s name any component of the Entry, without such Eligible Entrant reserving any 
rights or claims with respect thereto.  Sponsor shall have the exclusive right, in perpetuity,
throughout the Territory to change, adapt, modify, use, combine with other material and 
otherwise exploit the Entry in all media now known or hereafter devised and in any manner,
in its sole and absolute discretion, without the need for any payment or credit to Entrant.

So the game will become the sponsor's property; however, they don't ask for source code. So will I still own the rights to the source code, whatever that means? And if it doesn't win said competition, will I be able to publish it myself without their trademarks? I am very new to software legality stuff, so I would appreciate any clarification.

Since there's a possibility I won't even own the source, is it possible to make the game core engine open source software with a not-very-restrictive license and include that in the project, so I at least still own the game engine? Or does it not work that way?