I'll use Qt as an exmaple:

If I use Qt for a commercial software, I have to consider the Qt licensing, but at the same time Qt states many own third party components with different FOSS licenses. e.g.

Each of those third-party dependencies may have its own dependencies with different licenses. And each of those dependencies may have...

Now if I want to release an application (commercial license) that uses Qt under LGPL (as a shared library), is it sufficient to comply with LGPL for the "first-level" (Qt), i.e.

  • provide the LGPL and GPL license
  • state the third-party component used
  • describe a way to exchange the Qt shared lib
  • if my GUI shows copyright notices, also show Qt's copyright/license


Or will I have "recursively" to dig into Qt's third-party components, and provide the license and maybe source code for each of those?

Of course this question is not limited to Qt, but to third-party components in general which make use of other third-party components

  • 3
    Yes, in general you must fulfill all license obligations. But the Qt project uses only 'compatible' third party code. For example, none of the third-party projects on the page you mentioned would require you to supply separate source code. Complying is done in the way Qt have shown (by providing a documentation page for it). However, suppose you added a third party library to make an 'enhanced' Qt and suppose that extra third party library had a GPL license. Now, anyone using your enhanced Qt would have to comply with that project's license as well (GPL), even if 'enhanced Qt' is still LGPL.
    – Brandin
    Mar 6, 2018 at 15:28


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