Imagine the following: Some one posts on SO and describes in his post something by an embedded picture.

This is (as non special licensing or CR was mentioned) same as publishing as CC-BY-SA. But what now if the poster wasn't allowed to do so? What if I'm expecting he was (everything else would destroy the idea of open source) authorized to do so and used it in a way, that the original license, CR and limitations would have forbidden.

Would I be liable for it? If so, how to protect against?

2 Answers 2


If you had a reasonable belief that the author who licensed the work was entitled to do so, you have an absolute defence to a claim of copyright infringement.

To your specific scenario, if someone posts their content on Stack Overflow and a reasonable person would believe that it is their submission and that they are licensing it under the CC-BY-SA licence, and then you then go on to use it, you have a defence against a claim of copyright, even if the person who posted it did not have the right to licence it in that manner.

An injunction to prevent your continued use of the work is likely to be granted, however you would likely not be liable for damages or monetary reparations.

  • I'd be careful with "reasonable belief". If I see you driving a car, I have a reasonable belief that you own it. If I buy your car, I need to see the right paperwork to have a "reasonable belief". If you use someone's code, which would be a rather serious case of copyright infringement if the person giving you permission had no right, then you need to be quite careful before you have a "reasonable belief" that everything is fine.
    – gnasher729
    Commented Dec 23, 2015 at 23:18
  • The terms of Stack Exchange sites require users to license their contributions under CC-BY-SA. As users of the site, a reasonable person would believe that someone who is a user of the site and contributes their content to it is aware that they are licensing the work as such. Barring evidence to the contrary, I would generally (and in my opinion, reasonably) believe that people using have the right to do so, because the terms of the site which all users (but especially registered users) must adhere to when contributing content require them to have such rights.
    – jimsug
    Commented Dec 23, 2015 at 23:28
  • And someone who steals other people's code and claims to have written it himself would be stopped by the terms of Stack Exchange? I don't think so. It's illegal to sell stolen cars as well - doesn't mean that you can trust anyone who sells a car without some checking.
    – gnasher729
    Commented Dec 24, 2015 at 0:56
  • I reject your specific analogy with respect to motor vehicles, as in most countries in the world it is reasonable to expect that there will be a registry recording vehicle ownership and title and as such a duty to check them may be reasonable. Does such a registry exist for code? No. However, I accept your comment about the fact that anyone can use copyrighted material. This is the case everywhere. However, if someone provides code in an answer on Stack Overflow, barring evidence to the contrary, I would personally say that you could reasonably expect that they have the right to do so. ...
    – jimsug
    Commented Dec 24, 2015 at 1:15
  • ... If other people commented and said that it was stolen from some other source? Or, perhaps, if it could be proven that I had seen the code in some other answer and it stated that it was copyrighted? That might defeat such a defense. Of course, this is all conjecture unless/until we can find a court ruling that says something one way or another, right? I'd say that my point - about the existence of some authorised, official registry - might impose a greater duty when acquiring goods or services.
    – jimsug
    Commented Dec 24, 2015 at 1:16

From the example you've provided, I gather the question you're asking is "what happens if someone publishes something that they're not licensed to publish?", is that correct?

If so, I believe the answer is "mostly nothing". A third party publishing (or republishing, really) content in a context where they implicitly or explicitly agree to license the content to others, when they have no license to do so from the owner of the IP in question, would be a straightforward violation of copyright in most jurisdictions. It has no impact upon the terms that the content is licensed under.

For instance, if I find some GPL'ed code on github and copy/paste in onto SO, that action doesn't have the effect of removing the GPL from the code. The license terms are whatever the original author of the code specified, and unless they give permission to relicense their code under CC-BY-SA (or soon, MIT) then 1) no such relicensing happens just because I post their code, and 2) it's not technically valid for me to be posting their code like that in the first place.

In principle, the owner of the IP could sue for injunctive relief (and possibly damages) in most jurisdictions in such a case, both against the person who illegally republished their IP and against anyone they find using it (saying "I found it in a post on SO, which means I can use it if I want" should protect you from being liable for damages but won't let you keep using the IP without a license if you can't show that 1) the plaintiff published their content on SO, or 2) the plaintiff gave somebody else permission to publish their content on SO). In practice, however, it's relatively uncommon for such litigation to be brought, and even less common for such cases to actually proceed to trial.

Which brings us back to "mostly nothing". If the owner of the IP never finds out that their IP has been illegally republished, then certainly nothing happens. Or if they do find out, then they might request that the content be removed. Or negotiate licensing terms with anyone using it. Or if they're particularly militant and have deep pockets and can see an upside to litigation, maybe they'll sue. However that last outcome is generally unlikely unless the violation is particularly egregious, or if their takedown requests go unheeded.

  • But this contradicts with @jimsug 's answer, doesn't it?
    – Zaibis
    Commented Dec 23, 2015 at 12:12
  • 1
    The legal part of this answer accords with mine, that is: you will be protected from damages a reasonable person would believe that the IP was licensed, and that this wouldn't prevent a court from ordering an injunction to require you to cease using the IP.
    – jimsug
    Commented Dec 23, 2015 at 12:34

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