OpenCL is not an OS level API. I guarantee you they were basically just redistributing Intel and NVidia implementations. GCD isn't OS level either, it's just a library, but it is at least a new API.
OpenCL was created and open sourced by Apple.
>OpenCL was initially developed by Apple Inc., which holds trademark rights, and refined into an initial proposal in collaboration with technical teams at AMD, IBM, Qualcomm, Intel, and Nvidia.
OpenCL 1.0 released with Mac OS X Snow Leopard on August 28, 2009.
I'm talking about the GPU OpenCL implementation. Implementing OpenCL on the CPU is not really a big deal. I can guarantee you that these implementations were Intel and NVidia and were just redistributed.