You said: "There is nothing stopping a licensee from building coherent HyperTransport:"
Yes there is! They would have to licence it from AMD and not contravene patent law. There are numerous patents on cHT. Just reverse engineering it doesn't make it right. Being a licensee of HT doesn't confer any rights on cHT. Intel could try to develop a coherent PCI-Express and I think they will, but they can't just copy cHT