[AnIdiotOnTheNet]

https://github.com/torvalds/linux/blob/master/Documentation/...

> So, if you have a Linux kernel driver that is not in the main kernel tree, what are you, a developer, supposed to do? [...] Simple, get your kernel driver into the main kernel tree (remember we are talking about drivers released under a GPL-compatible license here, if your code doesn't fall under this category, good luck, you are on your own here, you leech).

In order for a driver to be in-tree, it has to be open.

Incidentally, this document is full of the kinds of arrogant and user-hostile arguments that the Linux community is known for, for example: "You think you want a stable kernel interface, but you really do not, and you don't even know it."