The full AMD hybrid stack with OpenCL, OpenGL, and Vulkan is now available. The focus is on Vulkan support while the whole stack will be improved. The binary bits are all isolated to user-space while riding atop the AMDGPU DRM kernel driver in the mainline tree. Given the AMDGPU focus, this is currently only working for GCN 1.2 GPUs like the Tonga and Fiji hardware.
This initial driver is in preview form but Ubuntu hopes to have it in a production driver with a "distro-packager-friendly license" in time for Ubuntu 16.04.
More details via this forum thread by AMD's John Bridgman along with the download links. Benchmarks coming.