GNU doesn't define the Linux kernel API. The kernel defines the kernel API. Applications (GNU whatever) use the API. Now Windows implements the API. The Linux kernel API. It doesn't implement GNU API because there is no such thing. See?
Linux kernel is the implementation of the kernel API. You can run Linux applications as long as you have the implementation of the API. Windows has it. Linux kernel has it. GNU doesn't have it. See?
GNU doesn't define the Linux kernel API. The kernel defines the kernel API. Applications (GNU whatever) use the API. Now Windows implements the API. The Linux kernel API. It doesn't implement GNU API because there is no such thing. See?
Linux kernel is the implementation of the kernel API. You can run Linux applications as long as you have the implementation of the API. Windows has it. Linux kernel has it. GNU doesn't have it. See?