Although stealers would like to be the only ones to service your car, I don't think they'd get past the Sherman Anti-Trust Act. Then again, Bill Gates has been able to get away with it, so who knows what the future holds.
GPL is an attempt by programmers and engineers to keep corporate greed in check. Think Linux and how hard Bill Gates and Micro$oft have been trying to squash it on a daily basis, for years now.