Under the old cc-by-sa 3.0 license, Stack Exchange's license to show contributions is potentially perpetual, but violating the license, it gets revoked. This follows from the definition of "You":

"You" means an individual or entity exercising rights under this License who has not previously violated the terms of this License with respect to the Work, or who has received express permission from the Licensor to exercise rights under this License despite a previous violation.

and is also covered in the Creative Commons FAQ. Even after an accidental violation that is prompty corrected, explicit permission is needed from the contributor to reinstate the old license.

How does this play with the new license that SE intends to require for new code contributions? What happens when a user takes code from one of the many old cc-by-sa-licensed answers, and posts it in a new answer? That someone else has no rights to relicense it. As a result of that user's action, SE will be distributing it in a way not permitted by the copyright holder (the original contributor). Doesn't this mean that SE too will at that point be in violation of the cc-by-sa license and have its license to the old code revoked?

Am I totally off base here? If not, is this a problem SE intends to fix somehow, or will it just be ignored in hopes that it doesn't come up with any important content?

  • The use of "you" in this post is intended to refer to Stack Exchange?
    – jscs
    Commented Jan 14, 2016 at 21:42
  • @JoshCaswell Yes. Would it be clearer if I refer to SE in the third person? If so, I'll edit.
    – hvd
    Commented Jan 14, 2016 at 21:45
  • Please do, that would be much clearer. It's a bit hard to tell if you're addressing SE or the reader.
    – jscs
    Commented Jan 14, 2016 at 21:48

1 Answer 1


Disturbingly, yes.

After another read through of both licenses, it appears this is possible.

In the 4.0 licenses, your rights under the license are automatically reinstated if you correct this failure within 30 days of discovering the violation (either on your own or because the licensor or someone else has told you). Under the 3.0 and earlier licenses, there is no automatic reinstatement.
CC FAQ, emphasis mine

Since SE uses the 3.0 version, your first point that the license is permanently revoked without explicit reinstatement is correct.

Your second point, that a re-post of old code would violate the old CC BY-SA license is also (more obviously) correct: without even reading the legal code, we know that BY-SA is copyleft and requires re-sharing to be done under the same license. A re-post of code would not be under BY-SA, thus would break the license terms.

This means overall that an accident or unknowing re-post of old-license code could lead to you losing your right to use that code. There is nothing in SE's terms that prevents this happening.

  • 1) Stack Exchange would not be responsible for license violations committed by another person. 2) The content cannot be relicensed just by being reposted. The original CC-BY-SA license still applies. It might appear, if attribution was lacking, that the content was available under MIT(crayon-SE), but that would not be so. Just as you cannot relicense, e.g., emacs, by posting it in your own Github repo, you cannot relicense someone else's SO post simply by copying it into your own.
    – jscs
    Commented Jan 14, 2016 at 21:46
  • "could lead to you losing your right to use that code" Can you clarify which entity you're referring to with "you" here? The only person who loses the right to use the code is the violator of the license.
    – jscs
    Commented Jan 14, 2016 at 21:47
  • 1
    @JoshCaswell You're not quite right. (1) No, they wouldn't, that's not what I'm saying. (2) Actually, yes you can. Come over to Open Source and ask if you like. By re-posting, the re-poster is representing that they have the right to distribute the code under MIT (because by then, new posts are licensed under MIT), which they don't. Thus, they violate the license.
    – ArtOfCode
    Commented Jan 14, 2016 at 21:49
  • Yes, they violate the license. They don't change the license.
    – jscs
    Commented Jan 14, 2016 at 21:52
  • @JoshCaswell Stack Exchange could sue the user for violating their terms of service, but they are still responsible for hosting the content on their website (I think). They would sue for their lost revenue due to be taken down, but it would still be bad. Commented Jan 24, 2016 at 0:19

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