Comment by belorn

There is a big difference between a company distributing a proprietary Linux driver, and the linux project merging software of a gpl incompatible license. In the first case it is the linux developers who can raise the issue of copyright infringement, and it is the company that has to defend their right to distribute. In the later the roles are reversed with the linux developers who has to argue that they are within compliance of the copyright license.

A shim layer is a poor legal bet. It assumes that a judge who might not have much technical knowledge will agree that by putting this little technical trickery between the two incompatible works then somehow that turn it from being a single combined work into two cleanly separated works. It could work, but it could also very easily be seen as meaningless obfuscation.

> Why are all drivers expected to use the GPL

Because a driver is tightly depended on the kernel. It is this relationship that distinguish two works from a single work. A easy way to see this is how a music video work. If a create a file with a video part and a audio part, and distribute it, legally this will be seen as me distributing a single work. I also need to have additional copyright permission in order to create such derivative work, rights that goes beyond just distributing the different parts. If I would argue in court that I just am distributing two different works then the relationship between the video and the music would be put into question.

A userspace software is generally seen as independent work. One reason is that such software can run on multiple platforms, but the primary reason is that people simply don't see them as an extension of the kernel.