Radeon Rays 4.0 Released - Adds Vulkan While Dropping OpenCL, No Longer Open-Source
Radeon Rays 4.0 adds Vulkan API support as well as DirectX 12 and HIP capabilities, but now drops OpenCL support given HIP and DirectX12/Vulkan. Radeon Rays 4.0 also still supports CPU-based execution too.
Radeon Rays 4.0 also has various other improvements to this ray intersection library.
But sadly with Radeon Rays 4.0, the library is no longer open-source. Radeon Rays 2.0 is open-source but moving forward it looks like Radeon Rays is not open-source, but whether that is just a temporary obstacle or a long-term plan isn't clear at the moment. Though rather surprising given the nature of GPUOpen and their other software releases.
More details on the new Radeon Rays 4.0 via GPUOpen.com and the project's GitHub where at least the 2.0 "legacy" code remains available under the MIT license.
Update: AMD now says they will be open-sourcing it as a result of community feedback.