I'd say voice clips from stream are regarded as public domain or fair use in this case, so there's no issue there.
In-terms of things like characters, designs and names, those are more abstract concepts than actual game-used assets like models and sprites, meaning they're considered beyond the scope of the rule and are allowed. Basically, if you make a Scoot, you can add a Scoot.
The asset rules will probably be made less strict if we do another one of these jams, just keeping things a little restrictive for now to make things easier on the mod/judge team while they get used to the whole game jam thing.