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From the Wikipedia article on Linux:

The Linux kernel is licensed explicitly only under version 2 of the GPL, without offering the licensee the option to choose "any later version", which is a common GPL extension. There was a debate over how easily it could be changed to use later GPL versions such as version 3 and whether this is even desirable.

But I've visited the current COPYING file and that doesn't mention it. So, considering the following text in the file:

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

So, can Linux be released under GPLv3?
(or say I want to know can GNU release linux-libre under GPLv3?)

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When this question was asked, the kernel's COPYING file started with the following comment (second paragraph):

Also note that the only valid version of the GPL as far as the kernel is concerned is this particular version of the license (ie v2, not v2.2 or v3.x or whatever), unless explicitly otherwise stated.

Nowadays it says, more succinctly,

Being under the terms of the GNU General Public License version 2 only

with references to the GPL-2.0 and Linux-syscall-note files, the latter of which carries the first notice above.

Parts of the kernel are licensed with "or later" (e.g. joydev.c), but many files only mention version 2 (e.g. apm-power.c). So the kernel as a whole is licensed under version 2 of the GPL only.

Linus Torvalds is famously unhappy with version 3 of the GPL, so even if it were feasible (which it isn't, given the number of copyright holders), as long as he is "in command" there's little chance the kernel would be licensed under any later version of the GPL.

The part you quoted (which can still be seen in the renamed file) is part of the “How to Apply These Terms to Your New Programs” section of the document, and explicitly comes after the “END OF TERMS AND CONDITIONS”. It can’t be construed as applying to the code in the repository.

See also the detailed kernel licensing rules.

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  • 1
    @StephenKitt what's the difference between both COPYING files? – Pandya Jun 25 '16 at 17:50
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    @Pandya the file you linked to is very old (1994), and was updated at some point prior to the git import to the version currently in the source tree. I'm not sure why kernel.org/pub/linux/kernel/COPYING was never updated... lkml.org/lkml/2006/1/25/273 gives additional info. – Stephen Kitt Jun 25 '16 at 18:06
  • @StephenKitt the right place to look is here, in the git tree: – Philippe Ombredanne Jun 25 '16 at 22:57
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    @PhilippeOmbredanne it appears the end of your comment got lost somewhere... – Stephen Kitt Jun 27 '16 at 13:28
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    my bad: and anyway you answer had the correct link anyway. Re: kernel.org/pub/linux/kernel/COPYING you should post to LKML to suggest an update... This file likely is not under a Git repo and hence was never updated? – Philippe Ombredanne Jun 29 '16 at 14:52
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The part of the COPYING file which says this is in the appendix which gives GNU's recommendations for how to apply the license. Just because they recommend that authors use that text and allow their software to be licensed under future versions doesn't mean all authors have to do so! Linus Torvalds decided he would not, and so the kernel is licensed only under the GNU GPL version 2.

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  • My question doesn't ask whether we've to do so or not, rather it asks can we do so or not! – Pandya Jun 26 '16 at 4:23
  • @Pandya That's exactly what I've answered! Your question is based on a faulty premise because the license doesn't contain that phrase, only the appendix. – curiousdannii Jun 26 '16 at 6:35
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    @Pandya The excerpt you quote in your question is not part of the terms of GPL license grant, so it has no bearing on the code's license terms. The answer to your question appears to me to be "The text you quoted does not appear in the license terms or license grant by th eauthor, so any conclusions based on the assumption that it is part of the license are unfounded". If pointing out the absence of those terms is not an answer to your question, then we may not understand what your question is; you might need to clarify further. – apsillers Jun 30 '16 at 23:09
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The question, as stated, is:

Can the Linux kernel be released under GPLv3?

Yes, of course. If all the copyright holders involved agree to release the kernel under GPLv3, or any other licence, then they can do so.

But the real question seems to be:

Can the Linux kernel be used under GPLv3?

As the question stated, Wikipedia says “no”. So what about that COPYING file? I will come back to that, but first, let us get this out of the way:

can GNU release linux-libre under GPLv3?

No, GNU (which presumably refers to the FSF) cannot release Linux-libre under any licence (other than GPLv2), because they are not the copyright holder and the copyright holders have only granted permission for GPLv2.

Now, back to that COPYING file. The current version is just a stub, but there is a snapshot dated 12 April 2016 in the Wayback Machine. This snapshot did indeed contain the text quoted in the question; what does this mean? Nothing, by itself. We need to consider the context of this text.

By convention, a licence or licence notice in a file called COPYING in the top level of a repository applies to that repository, unless otherwise stated. In this case, it was otherwise stated:

Appendix: How to Apply These Terms to Your New Programs

To do so, attach the following notices to the program.

This makes it clear that the text quoted was merely instructions for applying a licence, not the actual licence for this repository.

The copyright holders took no other action to apply GPLv3, so no, the Linux kernel cannot be used under GPLv3.

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