This is a different animal. This is not a joint effort. More like a spit in the face. Think of this as an evolution of the tactic used by NVidia when they came out with physx. They said they there is nothing stopping AMD from using physx, except most likely royalties to NVidia (which is also a common practice), but most of us seen though that as a ploy, good old marketing to help build NVidia's image and diminish AMD's. This, is of course different in terms of tech, but the same in term of business. Even better actually because they get to claim that it's open and there is nothing stopping NVidia from using the API.