That quote seems to be from the README's subproject listing section: "liboslexec, a library that implements the ShadingSystem class, which allows compiled shade

That quote seems to be from the README's subproject listing section: "liboslexec, a library that implements the ShadingSystem class, which allows compiled shaders to be executed within an application. Currently, it uses LLVM to JIT compile the shader bytecode to x86 instructions." But this doesn't preclude GPU use of the language.