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My software project is using several third party libraries which have different licenses (LGPL, MIT, BSD). I distribute the dlls of those libraries, and I understand that I need to give license information and if the license demands it (like LGPL) acknowledge the use.

I sometimes see, that some programs have separate copyright sections, where they list the copyright holders of the third party licenses? Is this necessary?

  • Is your software a library or an application? The licenses of your dependencies only matter when you give someone a copy of these dependencies, and that's usually only an issue if you provide an installer or pre-built application. – amon Dec 7 '19 at 21:19
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Yes, you need to do this. Most of the licences you list don't demand a general-purpose acknowledgement, they specifically require that the copyright notice be preserved; this is often seen as sufficient acknowledgment, also.

BSD 3-clause says:

Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

MIT X11 says:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

and LGPLv3 says:

For a Combined Work that displays copyright notices during execution, include the copyright notice for the Library among these notices, as well as a reference directing the user to the copies of the GNU GPL and this license document.

LGPLv3 does have a more general "prominent notice" requirement, but the requirement to preserve copyright notices is sufficiently widespread that preservation of them all is a good idea, as well as courteous to those authors - as if your work is a derivative of theirs, then they actually do have a copyright interest in it.

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  • The GPL (and LGPL, by extension) also has a requirement about preserving "Appropriate Legal Notices". If applicable these could also apply to some functionality of the program like a command line option or menu command which display copyright information. However many programs (e.g. non-GNU programs) do not have any such notices built-in, so the requirement is not relevant. The "Promiment Notice" language requirement only applies to source code. – Brandin Dec 6 '19 at 7:43
  • @Brandin LGPLv2 has no such requirement that I can immediately find; GPLv3's (which I acknowledge LGPLv3 doesn't waive) only requires them in interactive mode, and then only if that facility was already present. The point I was trying to get across was that although *GPL's requirements are a bit more complex than those of the non-copyleft licences, the latter definitely require preservation of copyright notices, and even if it turns out not to be strictly required by *GPL it would be no bad thing to preserve them for *GPL content also. – MadHatter Dec 6 '19 at 8:00
  • Regarding BSD: This for sure is true for source code, but what if I only ship the resulting dll? LGPL: Yes, thats clear MIT: Does this mean when distributing source code or dlls? – maxwell Dec 6 '19 at 10:58
  • @maxwell I've quoted a different bit of the BSD licence that should make it clear that it applies to shipments of the DLL (ie, binary form). The MIT licence also means all copies, not restricting things to source code. – MadHatter Dec 7 '19 at 9:12

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