The memory that XNU and Darwin are technically open-source projects is a curse that brings one only suffering.
I would call them open access. Apple doesn't accept contributions.
Does not accepting contributions make you not open source? I would assume if the license allows you to fork it, that makes it open source (as opposed to "shared source" licenses that basically say "look don't touch")
I feel like Apple wouldn't want to make full Linux work on their hardware, but they could enable their Darwin kernel to emulate Linux syscalls and provide a way to boot into a mode that basically loads the kernel and whatever Linux shell you want
This path is already taken and it didn't sell Apple hardware in masses.