> The way I see this:
> There is a copyright enforcement scheme.  (A simple test for
> the word GPL.) Trivial, but still an enforcement scheme.

If this were true, then the Linux kernel with it could not be distributed.

If it were a legal mechanism to prevent people from modifying modules, then 
it's a further restriction. Whoever distributes a Linux kernel with a copyright 
enforcement scheme (assuming it includes at least one module) is violating 
section 6 of the GPL.

Adding a copyright enforcement scheme to the kernel, and then distributing it 
with modules that cannot be modified in some ways because of that scheme, is 
imposing a "further restriction". (Since the GPL does not contain the 
restriction.)
 
> You are of course allowed to remove the test completely,
> as the GPL lets you change the kernel source in any way you wish.

It also lets you change the modules in any way you wish. I can't see how you 
can have it both ways. How is removing an enforcement scheme not circumventing 
it?
 
> But you are still not allowed to circumvent the scheme as long as
> it is in place - in those parts of the world were circumventing is
> illegal.

If that's true, then the Linux kernel cannot be distributed in those parts of 
the world where circumventing is illegal. The GPL does not prohibit 
circumventing anything, so the DMCA (as invoked by those who added copyright 
enforcement schemes to the kernel) would be them imposing a further restriction 
on our right to modify the modules included with the kernel.

> So a vendor using the \0 trick is on very shaky ground. 
> He has another option - to patch out the test.  But he
> don't want that, for then he have to distribute a kernel,
> not only a module.

The GPL does not permit you to (ab)use the law to prevent people from modifying 
GPL'd works. If a law prevents people from modifying GPL'd works, then those 
works cannot be distributed where that law applies.

You can certainly argue that this doesn't make sense if the law is not 
deliberately invoked. For example, some countries have a law against denying 
the Holocaust. I don't think you can rationally argue that no works are 
disrtibutable under the GPL there because someone can't legally modify those 
works to deny the Holocaust.

But the assumption that the GPL linkage code is a copyright enforcement scheme 
would mean that the Linux kernel would have been deliberately modified so as to 
invoke a law that prevents people from modifying GPL'd works -- including the 
modules included with the kernel itself. If that doesn't make the kernel 
undistributable, the GPL clause 7 doesn't mean anything.

" For example, if a patent license would not permit royalty-free redistribution 
of the Program by all those who receive copies directly or indirectly through 
you, then the only way you could satisfy both it and this License would be to 
refrain entirely from distribution of the Program. "

It seems to me that another example would be if the DMCA does not permit 
modification of portions of the Program, then you cannot distribute the program.

This is the way the GPL's "self destruct" mechanism is supposed to work. For 
example, if someone claims there's a patent that prevents some piece of the 
Linux kernel from being used freely, the GPL is designed to force Linux 
developers and distributors to hack that piece out of the kernel so that the 
program can remain free to distribute and modify. It actually *fixes* legal 
problems by prohibiting distribution until the distributors can figure out how 
to get people's GPL rights back.

The way out of the GPL problem is to make clear that it is *not* a copyright 
enforcement scheme, it's simply a notification scheme. Claims and actions in 
another direction threaten the distributability of the Linux kernel, and 
frankly violate the intent, spirit, and precise language of the GPL.

DS


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