“One of the big problems with Prodkernel is that it detracts from upstream participation, he said.”
Google runs its data centers on an old kernel with 9000 patches stacked on top. Every two years or so it drags them forward to a newer kernel. Its bug fixes help nobody else because they apply to a years-old kernel. Google took everything from Linux and kept its improvements in a private fork. Project Icebreaker is the bill coming due.