Werrd licenses the Stack technology from YYF. The way I understand it, Duncan does not use the same tactic of keeping the stack in place, and that is what the YYF patent is, the way to hold the stack in place. YYF will be the first to admit that they are not the first to come up with spinny things on the side of yoyos.
Expanding on this, the stack grips look ALOT like zstacks, but aren’t. It is complicated, and best left to patent attorneys, of which I am not.
Well the idea behind the center track bearing is pretty close to the konkave, and during worlds yoyofactory did give away “spin top buttons” that worked conveniently well as a counter weight which duncan has the rights too. And lets not forget the metal weight rings in the new line of yoyofactory plastics that resemble the rings in the buzzon element x’s. I’m not trying to say anything bad about yoyofactory and I’m not saying Duncan’s use of the spinning side caps is completely justified either, but hey companies are gonna borrow/expand upon good ideas and these spinning side caps aren’t the first time this has happened.