Noob question I guess but just to be sure.  Is it game-legal to use assets created by third parties, such as models, sprites, shaders and etc?

Thanks.

(Edited to fix a silly typo)

Under FAQ it says: 

Do I have to do everything myself?
Not at all! If you want to use public domain art/sounds or the like, that's entirely fine. And we encourage jammers to team up, too!

Thank you