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I am using a GPL licensed library which stated clearly that it is OK to link to it in commercial projects without the need to publish your own source code (as an exception to the regular GPL that force you to publish the source along with your product).

Let us call this library with an modified GPL license "Library A". Now, there is another library (let us call it "Library B") that link with the Library A. The Library B itself is licensed under GPL but without that exception which allow you to keep the source closed.

My question is:

Is licensing the Library B without this exception too a legal action? I mean since the author(s) of Library B uses Library A, doesn't this force them to add the exception to their library too?

In other words, can link to Library B in my commercial product with the need to publish my source?

closed as off-topic by Robert Harvey, amon, Jörg W Mittag, Bart van Ingen Schenau, gnat Jun 1 '18 at 11:26

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions asking for legal advice or aid are off-topic here. You may be able to get help with understanding, applying, and complying with free and open licenses on Open Source. You may be able to get help with legal terms, concepts, language, and procedures on Law." – Robert Harvey, amon, Jörg W Mittag, Bart van Ingen Schenau
If this question can be reworded to fit the rules in the help center, please edit the question.

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    The short answer is no. The library with the exception in its license does not give you a buffer against which you can link GPL'd libraries without triggering the copyleft provisions. Were that the case, you could simply write your own shim to disable the GPL license. – Robert Harvey May 31 '18 at 22:42
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You have some confusing terminology in there.

The GPL does not permit what you claim the library allowed you to do.

The LGPL (Lesser GPL, formerly Library GPL) does.

What it sounds like you are saying is that you have LibraryA that is LGPL, and LibraryB that is GPL, and you want to link BOTH of them to your commercial application without your commercial application contracting the GPL virus.

Sorry, Dave, you can't do that. LibraryA allows it. LibraryB says you have to GPL your source if you use it.

The original authors of LibraryB were OK using LibraryA, which was LGPL. They played by the rules. They COULD HAVE released LibraryB under LGPL, and they chose NOT to do so. Rather, they chose to release LibraryB under the GPL, which requires users of LibraryB to release their code under GPL, including making source available, and you are also required to play by the rules.

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    The GPLv3 allows the copyright holder to grant extra permissions, such as freely linking against that library. In fact, the LGPLv3 is implemented using this extra permissions mechanism. Another common permission is the Classpath Exception in Java code. Extra permissions were also routinely granted under other GPL versions. So it is perfectly possible for Library A to be under GPL + sone exceptions, without actually being under the LGPL. Your remaining analysis is still correct. – amon Jun 1 '18 at 6:08

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