I've just discovered that one of our old users (barrycarter, now "user21"), who is no longer with us, used a personal, unlicensed github repository in 31 of his posts: https://data.stackexchange.com/astronomy/query/1292675

It seems he has since deleted his account with github, and his repository along with it. While his answers do not technically rely on the contents of the repo to understand the answer (in at least the handful of cases that I checked), they do rely on the repo for users to be able to validate his answers in many cases.

This presents an interesting problem. In a sense, this is a subset of the broader issue of link rot, but it is unique because he never licensed his repo, which means that he still holds full copyright on that repo; and even if someone had saved a copy it would be illegal to share here.

This practice feels antithetical to the mission of Stack Exchange in creating an enduring knowledge base. Should we create clearer guidelines for the use of links to user-created external resources in posts here? If so, what should they be?

  • $\begingroup$ Just to clarify: user-created content embedded directly in the text of the post here would automatically be licensed and if a user tried to remove it, mods would treat that as vandalism and revert it. In this case, however, the content was not actually in the body of the post, the readers are just directed to it by hyperlink. $\endgroup$ – called2voyage Sep 9 '20 at 14:37
  • $\begingroup$ for this I've always used pastebin with expires=never as sort-of an imgur like thing but for code. I'm definitely for guidelines of the expires=never variety, and if github licensing makes something like that possible I think it's a great thing, exactly for the reasons you point out. $\endgroup$ – uhoh Sep 9 '20 at 14:55
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    $\begingroup$ @uhoh It depends on the license. If a user selects a non-revocable license for their content, then someone who had a copy of it could rehost it and it could still be legally shared here. $\endgroup$ – called2voyage Sep 9 '20 at 14:57
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    $\begingroup$ @uhoh The combination of the "expires=never" setting with the license the pastebin terms of service assigns to user content, does make that a good option! $\endgroup$ – called2voyage Sep 9 '20 at 14:59
  • $\begingroup$ @uhoh Though you should note, the pastebin license doesn't actually grant people the right to use the contents outside of pastebin, if that's something you wish to do. Linking to pastebin is fine, of course. $\endgroup$ – called2voyage Sep 9 '20 at 15:04
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    $\begingroup$ I use it only for short, fairly inconsequential scripts as a courtesy when it's not relevant enough to the post to even include as a code block, but might have some secondary educational value to some future reader. Big projects probably still need a git-like repository, and I suppose that SE posts that have some dependency upon them should really license accordingly, or not make them an important part of the post but only refer to them as supplemental information. $\endgroup$ – uhoh Sep 9 '20 at 15:09
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    $\begingroup$ @uhoh That's my feeling as well. $\endgroup$ – called2voyage Sep 9 '20 at 15:09
  • $\begingroup$ I just saw "the pastebin license doesn't actually grant people the right to use the contents outside of pastebin" again and the words finally sunk in, but the implications of that escape me. I'll read further... $\endgroup$ – uhoh Sep 12 '20 at 16:05
  • $\begingroup$ @uhoh For example, if you gave someone code, they wouldn't have a guarantee that you wouldn't sue them if they tried to incorporate your code into their own project. Or someone else could accuse them of stealing your code and get them in hot water that way as well, depending on the context. All the pastebin license ensures is that users of pastebin can read and operate pastebin functions on the content. $\endgroup$ – called2voyage Sep 14 '20 at 12:32
  • $\begingroup$ Okay, I think I've got that bit now, thanks! $\endgroup$ – uhoh Sep 14 '20 at 13:29

I think that the transient nature of everything on the Internet means this problem will always exist one way or another. So far I've only posted short Python scripts, so haven't needed to deal with this in my own answers.

  • I'd suggest encouraging users who post links to their own tools to provide a description of the core algorithms/techniques used in their implementation in their answers here. This would make it easier to create something that does a similar job should the need arise (either due to the external resource being removed, or if someone needs to use a different programming language/environment, et cetera). This would at least ensure that some of the essential details of the tools would be present on this site.

  • If the user posts a link to their own tool which does not have an explicit license, encourage them to supply one. I'm not necessarily sure this should be an absolute requirement, and I don't think pile-on licensing requests would be a good thing.

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    $\begingroup$ This sounds like a very reasonable guideline. I definitely don't want to make a hard and fast rule about licensing, as you say, but I do think we should encourage it. Thanks for putting in the effort to write an answer! $\endgroup$ – called2voyage Sep 9 '20 at 16:17
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    $\begingroup$ Here's a good resource to help selecting a software license, for those who are unsure of what would suit their project: choosealicense.com $\endgroup$ – called2voyage Sep 9 '20 at 16:24
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    $\begingroup$ And for non-software resources, here's a good tool for picking a Creative Commons license: creativecommons.org/choose $\endgroup$ – called2voyage Sep 9 '20 at 16:26
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    $\begingroup$ And here's a brief run-through of why licensing is important: choosealicense.com/no-permission $\endgroup$ – called2voyage Sep 9 '20 at 16:30
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    $\begingroup$ (Note: The above three resources are actually a good example of this. All three web pages are licensed under a Creative Commons license and are archived elsewhere on the web, such as the Internet Archive, so that even if they go down the resources will still be available and legally shareable here.) $\endgroup$ – called2voyage Sep 9 '20 at 16:51
  • $\begingroup$ @called2voyage those are excellent! $\endgroup$ – uhoh Sep 12 '20 at 16:01
  • $\begingroup$ On a related note, a recent Feature Request: Automatic insertion of license header for code blocks on SO meta was not well-received. It seems that people there are mostly happy enough with the CC-BY-SA license(s). $\endgroup$ – PM 2Ring Nov 7 '20 at 5:45
  • $\begingroup$ However, as I said in a comment there, Creative Commons recommend against using Creative Commons licenses for software. See here for details. We use CC-BY-SA licenses here because Stack Overflow posts are effectively a form of documentation that (may) contain code samples. They are not intended to be a primary software distribution mechanism. $\endgroup$ – PM 2Ring Nov 7 '20 at 5:46

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