CommonMark migration has begun!

Sites across the network have been scheduled for formatting migration, and some of them (Meta Stack Exchange included) have already finished their migration.

It was mentioned that this migration would not cause a license change. However, upon reviewing a low quality post, I noticed that the migration edit the Community user made to this answer caused a license change.

Could this be fixed?

  • 4
    I don’t understand this… This was the highest voted request on that announcement, and Yaakov explicitly stated “These edits will not cause a license change”. So why are these edits causing a license change now? Has this not been implemented yet, did the migration script misbehave, did staff just forget, or something else? What happened here? Jun 3, 2020 at 14:09
  • 4
    @user289905 I'm sure we'll get an answer soon. Yaakov's working on a large pull request for licensing fixes at the moment.
    – Spevacus
    Jun 3, 2020 at 14:12
  • 2
    Ah, okay, looks like this hasn’t been implemented just yet. I assumed that the license changes were already disabled for this migration before the edits took place. Jun 3, 2020 at 14:15
  • 3
    Kudos to you @ShadowKeepsSocialDistance for this awesome bounty message
    – Luuklag
    Jun 15, 2020 at 14:39
  • 1
    @Luuklag thanks, but alas.... turns out it's not a valid haiku! See Tavern for details of my shame. :) Jun 15, 2020 at 15:53
  • 1
    @ShadowKeepsSocialDistance Haikus don't necessarily need to have exactly 5-7-5 syllables - the one you typed is still valid. Jun 15, 2020 at 18:45
  • @Sonic for the support I thank you, better it makes me feel. Jun 16, 2020 at 5:47

1 Answer 1


This is now fixed. "Commonmark migration" edits no longer add licenses to their revisions in the timeline or cause the post revision to change. A backfill is being run to fix this for any posts where this is relevant.

on Markdown edit

a license spawned no longer

  • 4
    An unfortunate problem here is that once something has been published under a specific license, that's done. CC licenses are irrevocable, and the timeline seems clear enough for me to be free to use that content under the new license. Thus, while you can retroactively change that timeline, the content is available under CC BY SA 4.0, and that can't be changed.
    – Erik A
    Jun 3, 2020 at 15:52
  • 14
    @ErikA No, the content was never under version 4.0 – the license as shown is invalid for these automatic "upgrades". While SE seems to be fixing this to show the correct license, I'm amazed they are so laissez-faire about legal things, where “move fast and break things” amounts to commercial copyright violation.
    – amon
    Jun 3, 2020 at 17:18
  • 4
    @ErikA I wouldn't bet on that in court. As you can hardly argue that an automated edit, for technical reasons and technical reasons only, will be a derived work that warrants "new" licensing.
    – Luuklag
    Jun 3, 2020 at 19:41
  • 6
    @Luuklag The argument is simple: I saw this content, it said it was licensed CC BY SA 4.0 next to it, so I obtained it under a valid CC BY SA 4.0 license which is irrevocable. No matter the it was because of a minor edit, it got changed a couple of days later, etc. SE would have a case to retract it if they accidentally licensed it, but they didn't, they pushed the change knowing it would result in a licensing change. And it's hard to argue it's not licensed CC BY SA 4.0 if it says so on the site, especially if people unaware wouldn't have a clue that wasn't the intention
    – Erik A
    Jun 3, 2020 at 20:30
  • 6
    @ErikA, your argument doesn't hold, because the statement that the post was licensed under CC BY-SA 4.0 is false and thus you did not obtain a valid CC BY-SA 4.0 license and you can't argue based on the irrevocability of the license. You can only argue that you assumed the licensing information to be accurate and that you acted under the assumption of having a valid CC BY-SA 4.0 license. Note that the difference is only really relevant if your actions included things that are valid under the 4.0 version but not under the earlier version that is the actual license of the post. Jun 4, 2020 at 8:38
  • 2
    If someone has already acquired a post under the CC BY-SA 4.0 license, the site changing it back to CC BY-SA 3.0 doesn't revoke that license from them. So this really isn't a big issue. (Though switching to CommonMark wasn't such a priority that they couldn't have waited to have better tests to avoid this all from the beginning.) Jun 5, 2020 at 8:20
  • 6
    @curiousdannii and ErikA: Stack Exchange doesn't own any of the posts in question. They do not have the authority to unilaterally relicense under 4.0, so any such licenses are necessarily invalid. It would be as if I tried to give you a CC license for Mickey Mouse - I don't own that, so I can't license it to you.
    – Kevin
    Jun 10, 2020 at 21:20
  • 5
    @ErikA "The argument is simple: I saw this content, it said it was licensed CC BY SA 4.0 next to it, so I obtained it under a valid CC BY SA 4.0 license which is irrevocable". No, you did not obtain a valid license. SO does not have the legal power to grant you this license. They are displaying an invalid license. What you can do is suing them for damages if you rely on the shown license to be accurate and you actually had damages. A party can not grant you rights to a work that they don't own.
    – Polygnome
    Jun 11, 2020 at 10:25
  • 2
    @ErikA Assume the following: "Someone (a rogue employee, or a hacker) publishes MS Windows source code under a GPL license, I downloaded it and thus I obtained Windows under a valid, irrevocable GPL license". I hope you see that you did not gain a copy of MS Windows licensed under GPL in this scenario, because the one who uploaded it does not have the right to give it away under that license and thus can not confer these rights to you. MS still holds the rights, you have none. The same applies here, just that it isn't malicious, just incompetence to display the correct license.
    – Polygnome
    Jun 11, 2020 at 10:29
  • @Polygnome Yes, and that means any sensible business should treat content on Stack Exchange sites as if it had a constrictive license.
    – Roland
    Jun 11, 2020 at 14:41
  • Was this also fixed for earlier automated script edits (changeover from HTTP to HTTPS, as well as migration of MSO to MSE links)? Jun 15, 2020 at 18:46
  • 2
    @SonictheStay-HomeHedgehog yes. Please see the update to the licensing update post, which outlines all of the most recent changes. Jun 15, 2020 at 18:55

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