In this particular case, we're talking about a license clarification that gives you more rights than you otherwise could. So, if you hadn't read Linus's interpretation of his own license, you would think that you always had to GPL your LKMs. So there's no point in which Linus could actually sue you for not reading his LKML rants - they strictly increase what you are allowed to do under the license.

If this was the opposite case - say, Linus saying that the GPL required something that the text of the license said it didn't - then a judge would probably be inclined to not listen to Linus.

There's two fallacies engineers commonly get tricked by when talking about the law:

- "Code is law"[0]: the belief that legal protections, contractual clauses, and so on can be replaced with technical protection measures and "smart contracts".

- "Law is code": the belief that judges are merely human interpreters for an English-language-shaped virtual machine that contracts and laws are written in.

These fallacies are dual to one another; the root cause is a fundamental misunderstanding of how laws work. Judges are not merely tasked with executing a computer program in their heads; they are allowed and expected to actively comprehend and rewrite the law based on the facts at hand. "Legislating from the bench" is a deliberate feature, especially in "common law" jurisdictions where prior rulings are allowed to be treated as good as actual passed-by-Congress laws.

A good example of how this works would be Oracle v. Google. Strictly speaking, as much as we hate Oracle, they had the most meritorious argument, and they were trying to enforce the GPL. If you take copyright as a given on software, then that copyright can be applied to the thinnest sliver of creativity present in that software. Yes, even lists of function names and signatures alone should be copyrightable, and the GPL copyleft should trip if you copied them. However, the entire software industry did not actually consider these to be copyrightable, and acted as if they weren't. In fact, even Oracle's own cloud division was busy doing to Amazon what they were suing Google for doing to them. When SCOTUS saw this, they actively decided to change the law in favor of Google because it was the interpretation that most actual copyright holders in the industry had been operating on.

[0] With apologies to Cory Doctorow

Actually, if you only read the license files included with the kernel source, you'll be very confused and unsure of what you can actually do. The GPL is painfully vague, and there have been endless debates about how it applies to kernel modules, programs, etc. (such as this very one we're having now). (And I'm taking into account the clarification files in the source). Linus' LKML clarifications are post-hoc and not linked in the kernel files anywhere. I do agree with you that the GPL_ONLY "code is law" theory has some merit - and certainly a judge could use that as part of a ruling to uphold that interpretation. But I don't think that this aspect of the kernel license is going to be tested in court any time soon, so it's all speculation at this point.

The insane words are ones that you made up. The documentation is literally in the source code. If courts need to understand precisely what it means as it applies to a particular case, yes they can call Linus as an expert witness.