When AMD begun to release specs for its GPU, I've read a theory about the fact that this move was motivated by the project to release hybrid CPU/GPU by AMD. Indeed, AMD CPU were also successful because Linux users like AMD too. However if AMD release an hybrid CPU/GPU and that the GPU part is only supported by a binary driver, it means for AMD/ATI that most Free Linux distribution won't be able to support out of the box the AMD CPU/GPU and some Linux users may no longer buy AMD CPU because of this. So providing the doc, and allowing to have Free support out of the box was a must. As we could see, AMD is providing all the needed specs and microcode.