When a question or answer was posted under one license (e.g. CC BY-SA 3.0), and edited under a different license (e.g. CC BY-SA 4.0), who should be credited as the "author" for attribution purposes?

  1. The original poster only, specifying the earlier license?

  2. The most recent editor only, specifying the later license?

  3. The OP and the most recent editor, specifying the earlier license for the OP and the later license for the most recent editor?

  4. The OP and all editors, specifying the license for each of them?

From the recent Meta post on Creative Commons Licensing UI and Data Updates:

  • Every time a piece of content on the site is edited, the editor creates a new version of the previous version. The new version of that work is considered to be republished and therefore governed under the CC BY-SA version in effect as of the day on which the edit was made.
  • Each revision to a work creates a new version and is licensed separately. Thus current version of any piece of content (that appears on the site) is the most recent revision, and will have a license version based on the date on which that revision was published.

That kind of seems to imply Option 2 (attribute to the most recent editor only). But if so, the OP wouldn't receive any attribution for an edited post.

Option 4 would cover everyone, but it could get verbose if the post has been edited a bunch of times:

Stack Overflow question, "How do I exit the Vim editor?" 
by jclancy, licensed under CC BY-SA 3.0
Edits by Andrie licensed under CC BY-SA 3.0
Edits by jclancy licensed under CC BY-SA 3.0
Edits by Andrie licensed under CC BY-SA 3.0
Edits by Cole Johnson licensed under CC BY-SA 3.0
Edits by Nick Volynkin licensed under CC BY-SA 3.0
Edits by Peter Mortensen licensed under CC BY-SA 3.0
Edits by Peter Mortensen licensed under CC BY-SA 4.0


Stack Overflow question, "How do I exit the Vim editor?"
by Peter Mortensen, licensed under CC BY-SA 4.0,
based on post by Peter Mortensen licensed under CC BY-SA 3.0,
based on post by Nick Volynkin licensed under CC BY-SA 3.0,
based on post by Cole Johnson licensed under CC BY-SA 3.0,
based on post by Andrie licensed under CC BY-SA 3.0,
based on post by jclancy licensed under CC BY-SA 3.0,
based on post by Andrie licensed under CC BY-SA 3.0,
based on post by jclancy licensed under CC BY-SA 3.0
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    From a legal standpoint, everyone that contributed to the post is an author and must be provided with attribution. If space is at a premium, which it's usually not, then it's probably going to be considered reasonable, depending on their level of contribution, to say something like "by jclancy[link] and other contributors[link to edit history]". However, a strict reading of the license requires giving attribution to every contributor (i.e. option 4). – Makyen Jun 4 at 0:38
  • @Makyen Your idea of linking to other contributors by giving a link to the edit history sounds reasonable, but I wonder if that would require some sort of time stamp as well, because the number of editors can go up in the future. On second thought, that would make listing of each contributor a better option... – Tufkamt Jun 4 at 4:17
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    @Tufkamt I usually include a timestamp of when I copied something, or it's inherent in where I copied it to. The nature of SE posts, and anything on the internet, is that they change over time. When referencing, you really need to give a timestamp in one form or another. I feel I should reiterate that just a link to the edit history doesn't actually fulfill the attribution requirement, at least as I recall it. I'd need to re-read the license to be sure, but I don't think it does. – Makyen Jun 4 at 4:34
  • @Makyen I agree it’s best to include a timestamp for referencing an online work, since the content can change. But is it always required for copyright or licensing purposes? I know some software licenses require a copyright statement that specifies the year(s), but I don’t think that’s a requirement of Creative Commons licenses. – jkdev Jun 4 at 4:46
  • @jkdev Requirement, maybe, maybe not. Given that the inherent nature of what's being copied is that it can be changed by random people at any time, and that their doing so may impose a different license on the new version, perhaps even one after CC BY-SA 4.0, being specific as to which version was copied (i.e. when it was copied) seems like a good idea. – Makyen Jun 4 at 5:27
  • @Makyen What’s being cited can change. What’s being copied is a certain block of text content — the version of the post as it existed at a particular time — and that content has a particular set of authors. The copy and its authors remain unchanged even if the live post is updated. (To be clear, I’m talking about reusing content, not mirroring a live website.) – jkdev Jun 4 at 5:35
  • @jkdev Yes, if copied in it's entirety, including body, title, tags, formatting, etc., then someone could accurately determine which version was copied. However, it's a lot easier, and a lot more definitive, if you state when you copied it, or the revision ID. For example, what if someone makes just a tag change, which causes the license to change. Do you always copy the tags? What if what was changed was just code syntax highlighting (a body edit)? There are a variety of things which could be changed which wouldn't, necessarily, be obvious from a copy of just the displayed text. – Makyen Jun 4 at 6:09
  • @jkdev Yes, but we're in a situation where an edit to the post may change the license which is applied to the most recent version. While CC BY-SA 4.0 is, currently, the end of those changes, there's nothing that says there won't be a 5.0 or 6.0 in the future. Thus, in order to make it clear which license is in effect, enough information needs to be supplied to make it clear which version was copied, and thus which license, is in effect. That can be the most recent as of the date of the copy, or you might copy an earlier versions and need to specify that. – Makyen Jun 4 at 6:27
  • There are multiple ways all of that could be made explicit. A date doesn't have to be given, but even if not necessary, it helps support other information that indicates what happened. In other words, it's probably a good idea, but it's also probably not actually required. – Makyen Jun 4 at 6:27
  • @Makyen What I’m trying to work out is, what are the copyright/licensing requirements? If you omit the timestamp and other metadata, that’s less helpful for someone who wants to verify or look up your sources later on, but it shouldn’t make a difference in terms of complying with the CC license. – jkdev Jun 4 at 6:28
  • @Makyen In theory, if you copy a certain version of the post, your copy will remain constant and unaffected by changes to the original post, new editors, license changes, etc. As far as I’m aware there’s no CC requirement to keep your copy updated, or to give attribution to additional authors as the original post is updated. – jkdev Jun 4 at 6:34
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    @jkdev Yes, if you get all of the licensing, copyright, attribution, etc. correct for the copy you have made, then, no, you don't have to specify additional information. However, it may make the next person's life a bit easier. Maybe you've made some changes and someone else wants to copy what you have. Depending on their situation, it might be unreasonable for them to copy without doing due diligence and verifying where you got it. That may be a lot easier with more information than with the bare minimum. Having additional information reinforces the information already provided. – Makyen Jun 4 at 6:42

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