Gallium3D for AROS is brilliant but quite outdated, as it is the Nvidia 3D driver, which covers all DX9 oriented hardware from Nvidia and extends support to the DX10 Fermi architecture only. I am not sure if later GPUs are still natively working on AROS, but I'd sincerely doubt that. I'd not hope our Gallium3D library can hold OpenCL, whose first releases were somehow contemporary, but not in scope for the AROS port.
To be honest, all these components (MESA, Gallium3D, Nouveau drivers, GMA drivers) need a refresh to extend support to newer technologies and current GPUs. A more modern MESA implemetation should allow porting some version of OpenCL to AROS. The problem, however, would be: why? Is there any AROS software which would gain anything from a OpenCL port? Is there anyone willing to port OpenCL-based programs to AROS?