I think the bigger problem here is that there are no incentives for ATI to do the right thing. This closed API is merely taking something that was already closed and making it even more closed. There is no license that prohibits that, and there's nothing you can do about it.
I would love the idea if kernel devs started locking down the kernel against such abuse. I think this can be done by making the kernel symbols they are using in their proprietary driver GPL_ONLY. Give companies such as AMD a grace period of 2 years and if not fully open source by that time GTFO.
But since I don't see that realistically happening, I will save my own money for more open source friendly companies such as Intel.