the concept of "intellectual property" is philosophical in nature and, enough people believe/ed in it to build a legal framework to support it.
The way I see it, AGD needed a certain level of pre-requisite knowledge, obtained through prior ballistics, aerodynamics research, and their previously developed polystyrene, and then apply it to the challenge of making a frangible, round that is safe for recreational use. According to Tom, Perfect Circle Paintball fired thousands of rounds in their testing to get it right (fin angle, number of fins, location of center of gravity, denser fill). In my opinion, it would be pretty crappy for them to do all that research and experiment for some tool to simply make a mold of the round and then start producing them for less (because they didn't have to do the research.
I like to call it 'fin, spin-stabilization' but, technically, I believe it to be 'spin stabilization' since the round relies upon gyroscopic principles to maintain orientation rather than the fins themselves (like fins on a missile or rocket).