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GPLv2 clause 6

This week I was in Grenoble for the Embedded Linux Conference Europe. On the seond day of the conference — Friday — I was one of the few people wandering around in a suit. Even the guys who normally wear suits had dressed down to deal with the nitty-gritty of kernel threads, time sources, and boot time optimization.

So I talked about licenses. And license obligations. And interesting bits of the GPL version 2. There’s one clause of the GPL version 2 that I’d like to single out because it’s one that is surprising to me — and rarely mentioned. Clause 6.

6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

So, let’s suppose you (Bob) receive a program under the GPLv2 from the original author (licensor, called Alice), and pass it on unmodified to a third party, Charles. Clause 1 of the GPL applies, because it is verbatim. You just need to give Charles a copy of the license, and Charles receives a license from Alice automatically. There is in my reading no license, no relation whatsoever between you and Charles. Now if Charles distributes the program, the only license he could violate is Alice’s, and it is Alice who would need to enforce any violation.

This is actually how it works, too — suppose Alice wrote a part of the Linux kernel, she grants a license to any recipient (Charles) even though there are second parties involved (Bob); Alice can enjoin Charles to satisfy the requirements of the license. (For Alice perhaps read ‘Arald)

Now suppose you, Bob, modify the program before distributing it. In that case, clause 2b comes into play and the resulting work (based on the program) is also covered by the GPL version 2. When you distribute it, Charles receives a license from you to the modified work, and Charles receives a license from Alice to the original program. This is powerful, because Charles now has two licenses and two licensors that he must satisfy — but also weak, it seems to me, because Charles could violate one of the licenses and still keep the other. So if Bob sues Charles over compliance, Charles could just switch to the original Alice version (unless Alice enforces compliance issues as well).

It’s unlikely that would work in practice, because Charles wants the modifications done by Bob. Probably.

PS. Thanks to Saul Goode for some very careful and relevant comments to my previous writing on the GPL version 2; in particular pointing to the US Copyright Code and how it doesn’t restrict running the program at all — as indeed the GPLv2 itself writes “The act of running the program is now trestricted.”

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7 Responses to “GPLv2 clause 6”

  1. Michael "now?" Howell Says:

    “The act of running the program is now restricted.”
    Did you mean “not”?

  2. nonuser Says:

    Interesting… but irrelevant. You grew you case by saying that since Charles ends up with two licensors he would be in the position of violating any one of those without violating the other.

    But then, let’s go for the real case: given that Bob’s license can’t be any more restrictive than Alice (by means of 6. you may not impose…) you can’t violate Bob’s terms without violate Alice’s too. But because Bob can’t offer further rights over Alice’s work without Alice’s approval (common copyright laws), there’s no way you can violate Alice’s license without violate Bob’s too (with regards of the Alice’s part reditributed by Bob).

    So, in the end, there’s no way to reach your hipothetical case: with regards of the shared work you always will be in violation of Alice’s and Bob’s licensing terms at the same time.

    “if Bob sues Charles over compliance, Charles could just switch to the original Alice version (unless Alice enforces compliance issues as well)”

    Of course yes, so what? Are you implying to be a weak point specifically for the GPL that those without the means or inclination to enforce a licence won’t do it for the GPL case either?

  3. Bill Says:

    What? -Well that is just stoopid. Thanks for pointing it out. I stuck with GPL v1 and was thinking of switching to GPL v3 because of the proprietary use (forbidden) clause. I’m glad I never went to v2.

  4. Charles (really) Says:

    So in effect, my copy of Ubuntu is licensed to me by thousands of rights holders, each granting their own individual GPL to me? I can violate one person’s copyright, but still have all of the other licenses to fall back on?

    Somehow, I don’t think that’s quite right. I’m pretty sure that when you download or use code from a GPL-licensed project, there’s still just one license in play no matter how many authors the software has: either you’re granted permission by the copyright holders to use and distribute the software as specified in the GPL, or the license is revoked and the authors withhold all rights.

    It does bring up the interesting question of what happens to a project when only one contributor out of many wants to revoke the license to the portions of the program that they wrote. I always assumed that this can’t happen because a judge would ultimately say, “hey, you released the code under a permissive license, now deal with the consequences.” But I don’t know copyright law well enough to say that for sure.

  5. adridg Says:

    The hypothetical case was distributing binaries based on Bob’s work while offering the sources of Alice’s work. It looks murky to me whether you are violating Alice’s license or not.

  6. adridg Says:

    @3 – you cannot revoke a license on released code. Only on new versions or newer releases, so you can say “from october 20th, this is licensed as X” but any copies obtained before then are under the previous license and may continue to be used/distributed under the original terms.

  7. Vance Says:

    So in effect, my copy of Ubuntu is licensed to me by thousands of rights holders, each granting their own individual GPL to me?

    That’s exactly right. If you install the package linux-source and look at the top of randomly-selected source code files within, you’ll see copyright statements from a multitude of individuals. And that’s just for the kernel.

    This is why Harald Welte, if he intends to take legal action against someone (see gpl-violations.org), must ensure that the violator is actually using the netfilter code in the Linux kernel – because that’s the part he has copyright in.

    The number of projects where copyright is owned by a central organizing body (e.g., MySQL, OpenOffice.org, and many GNU utilities) is actually small, relatively speaking.