What I like about my Traxxas Sledge is, I can pick up parts for it from any RC shop and fix it in their parking lot. What I don't like about my Arrma Kraton is every broken part is an Amain order.
Judging by the fact some companies sell parts for Traxxas and others sell parts under code names for Traxxas I'd say what Traxxas is protecting is licensing rights. For a company as big as Traxxas leasing licensing rights for Traxxas aftermarket must bring in a healthy sum.