Is there any legal constraint saying that a commercial software must quote the open source libraries and public domain libraries regardless of the open source license type?

For example, let's say I develop a web application based on java servlet and I include (and use without modifications) a library licensed under Apache License 2.0.

Then I will sell my .war file that includes it.

Do I have to include a text file saying I am using it? What would/could happen if I don't?

  • If this is not the right place to ask, can you please point me to the right stack Exchange website?
    – ChaSIem
    Commented Oct 2, 2015 at 17:38
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    Why hello there! Your question is perfectly on-topic for the site. Have fun :)
    – Zizouz212
    Commented Oct 2, 2015 at 18:02
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    As a matter of courtesy, it is a good thing to include a thank you notice mentioning free software projects you are using, as part of a README or similar. (Yes, I know the question asks about legal requirements.) Commented Nov 1, 2015 at 13:25

1 Answer 1


It depends upon the license, and you can find out by reading the license. Many, such as Apache-2.0 require the license to accompany binary distributions, but some certified as Open Source don't. Some (for example zlib, libpng) ask politely for credit. libjpeg requires attribution, but in order to get certified as Open Source they promised not to enforce it.

  • Ok, let's focus on apache license 2.0 for example. If my software is not open source, do I have any obligation to my customer to explicit that I am using it?
    – ChaSIem
    Commented Oct 3, 2015 at 14:05
  • I am not saying not to maintain it. E.g. the jar file that I use, includes already its apache license file. My question is: do I have also an obligation to say somewhere that I use it?
    – ChaSIem
    Commented Oct 3, 2015 at 14:07
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    @GlennRanders-Pehrson Section 4.4 would indicate that you would have to display it within the application or in its documentation or some equivalent, at least as long as the copyright notice is in a NOTICE file. Commented Oct 3, 2015 at 15:04
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    @ChaSIem I don't think the remaining part of the question can be answered here. It's a legal question requiring your lawyer to interpret it. It depends upon your jurisdiction, whether "Moral" rights exist along with Copyright rights, etc. It has happened to me (redistribution of my software with attribution removed) and I didn't like it, but I don't have a battalion of lawyers enforce the license. Commented Oct 3, 2015 at 23:32

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