Since it is a distribution by a hardware vendor that ships NVIDIA GPUs, I'll assume that they got a licensed from NVIDIA to ship their operating system with the proprietary drivers.
Possibly, but what about the license of Linux? Surely nvidia.ko (being a derived work of both the GPL-licensed Linux kernel and the proprietary NVIDIA kernel object files) is non-distributable? Otherwise why does every other distribution faff around with akmods/DKMS, etc?