"assets that are freely licensed" is incredibly vague, what do you mean by that?
Assets -- meaning graphics, art, music, sound effects, color pallets. Anything that's not code*.
Freely licensed -- meaning things in public domain, or under a Creative Commons license or similar.
*You CAN use game engines like Godot, Love2D, even your own custom engine.
Thanks for the clarification.
According to some people here you are a bit of an expert on the topic.
Are CC-BY-SA-ND licensed works permitted? Can you use them in games and if so do specific conditions apply?