Sure but protect from what? Apple, Sony and Microsoft can just use BSD or any other proprietary kernel. Nobody will try to create the “new proprietary Linux” out of it because getting OS market share is hard even for an Open Source standard like Linux, let alone for some proprietary crap.

A potential issue is someone like Qualcom who makes their own proprietary fork which works on their hardware only. So instead of digging through the tens of thousand lines of code which Qualcom publishes for their out of tree Linux kernels, you can only reverse engineer. But again we are talking about a microkernel so most of these lines of code would be proprietary regardless. At least we save time of these crazy developers who try to bring out of tree stuff into mainline.