I'm a BSD developer, and I prefer to have a clear ISC licence at the top of every file that is fully self-sufficient in regards to the exact terms that I'm imposing on my work.

Is there a variation of the BSD licence that I could use for an open-source service with a web-interface similar to mdoc.su or mrtg, such that most or all deployments would be prohibited from removing a backlink?

Should I perhaps just add some such condition between the "Copyright" header and the terms of the ISC licence? What would be the shortest language that I could use, to ensure people comply easily, but also to ensure that it's not overly bothersome, either?

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    What backlink do you mean? I don't understand this question sorry. – curiousdannii Jul 7 '15 at 5:55
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    By "backlink" do you just mean attribution? Or attribution that specifically contains your website's URL, etc? It's not entirely clear what you're looking for right now. – Chris Hayes Jul 7 '15 at 6:24
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    When you are talking about a license which mandates that the user puts a link to your website: Such a license might not be very practical due to link rot. Your software might still be in use in 20 years, but your website might have moved or disappeared. Then licensees would either be forced to link to a non-existent website (or worse: to a domain which now hosts completely unrelated content) or be obligated to look for your new website, which is not a very reasonable request considering that it is hard to confirm for them that they found the correct website. – Philipp Jul 7 '15 at 12:11
  • I'm not proposing new links; just that existing links cannot be removed from the pre-generated or automatically generated pages. Also, link rot is already a problem with any licence -- the copyright header frequently has the email address of the author, and there's no guarantee that such address will keep on working, especially since some use university emails, and some dumb universities think that it's a great idea to disable and then recycle such addresses once one graduates. (So much for 40k$+ in debt!) – cnst Jul 8 '15 at 3:43
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    @Mureinik British spelling isn't a typo! – curiousdannii Dec 24 '17 at 22:26

AFAIK, there is currently no license having a slot reserved for a backlink URL that is recognized by the FSF or OSI.

It is not hard to create such a license. Adding a slot for the backlink URL to the ISC License and altering the permission statement as follows will do it.

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice, URL and this permission notice appear in all copies.

The ISC License is permissive, and recognized by both the FSF and the OSI. Your custom license will not have this recognition, and license proliferation should not be encouraged, so I do not think you should go on to create this custom license - but it is certainly possible to do so.

However, in free software project I generally find contact information helpful. This goes both for project email address and backlinks that points to project members or master repo. While link rot and email becoming a black hole is not unheard of, I still prefer to have access to contact information than not. This allows me to contact the maintainers to inquire about the status of the project, and to make pull requests if I've fixed a bug or added a feature. And even if the backlink URL leads to 404 or an unrelated site, it is helpful, because it is an indicator that the project is abandoned and if I want to continue using it, I may have to maintain it myself.

The license file is IMHO not the right place to put contact information. If you're community has standardized on the ISC License, please continue to use the recognized version.

Each free software project should have a README.txt with some basic information about the project, including any contact information you want to give your users. If your project does not have it, I suggest you create it and put the backlink URL there.

As for this part of your question:



You shouldn't worry about this. No serious developer will even think about removing this information as long as it is useful. Having some means to get in touch with the project's "home base" is treasured by free software developers. The link will not be deleted until it returns 404 or point to some cybersquatter's porn site.

  • interesting answer, but I think your sample suggested wording, "backlink URL", is somewhat ambiguous, because it might not be entirely clear what it refers to; for example, this case is specifically about web-based software; as an example of mdoc.su or lobste.rs (or even slashdot.org (although they adapted a different name for their engine)), it's both the "name" of the software, as well as the URL of the primary installation; what I want to do is possibly pre-emptively protect against the removal / replacement of the URL of such original installation – cnst Jul 20 '15 at 21:14
  • I used the phrase "backlink URL" in the example because the word "backlink" appears in the title of your question - so I thought it had some significance. I've changed it to "above ... URL". If there is only one URL between the copyright notice and the permission notice, it should be umambiguous what URL the term "above ... URL" refers to, provided the URL actually is an URL (http://mdoc.su/ not mdoc.su ). – Free Radical Jul 21 '15 at 3:06
  • It's now less ambiguous, but also more useless -- if I do include the URL in the copyright notice, then keeping it that way requires no licence modification in the first place. I'm talking backlinks within the actual source code. (Otherwise, the question would be just way too simple.) As such, your original is actually better, but I still think it's somewhat a bit too ambiguous. – cnst Jul 21 '15 at 14:41
  • I suggest that you update your question to spell out what you actually want. I am clearly not able to understand what it is you try to accomplish. – Free Radical Jul 21 '15 at 14:54


The license would simply need to have a sharealike clause. Then anyone else that uses it MUST share it with the same license (and link).

In the event the license does not have a "sharealike" clause such as some CC license you can put "a link to this license must be provided with all documents of this project" or some such wording.

  • Which share alike licence requires you to maintain links? I'm pretty sure they all allow you to change where the attribution appears. – curiousdannii Jul 8 '15 at 11:23

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