Does an open-source license depend on dependencies which are not part of a repo itself?

Question

In github I have a software repository which uses libraries at install time. These libraries are not included in the repository itself, but they are downloaded and installed when I install my tool (e.g. defined in setup.py for python projects).

Does the license I choose for my github software repository depend on any license of the dependencies?

And where can I find a webpage that explains exactly that? When I search for "how to choose a license for OS projects" nowhere the licenses of dependencies are mentioned. That might imply that my above question is answered by a clear "YES".

But is the an authoritative source somewhere?

Related question with unclear answer: Do the licenses of dependencies matter if the dependencies are not actually shipped by my software?

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Example: I have a github repository with one single file which is python code to create some graphics. This code is using two libraries the user has to install himself.

import external_library_to_compute_something
import external_library_to_plot_something

# Read data from a file here, ask user input

# Do some calculaions
# Maybe do some linear regression. Use a function of the first tool
a,b = external_library_to_compute_something.lin_reg(data)
# do some more calculations

# Now create the plot; use a function of the second tool
myplot = external_library_to_plot_something.simple_plot(plot_data)
myplot.show()

Do I have to consider the licenses of the two tools

external_library_to_compute_something
external_library_to_plot_something

YES or NO?

Answer 1

Yes, you have to consider the licenses of your dependencies.

After you modified your question and included the code example it is clear. You are using the "import" function of Python. This is an equivalent of Linking in other programming languages. Therefore your code perfectly matches the definition in GPLv3 "A “covered work” means either the unmodified Program or a work based on the Program."

If one of the imported modules is under GPL license, then you will have to put your own code under the same license. FSF is clear about that.

If the imported libraries have other licenses, then there might be a different impact, or no impact, on your selection of a license for your own code.

IANAL, and there has always been the discussion if the fact that you are not distributing the GPL-ed code yourself, but ask the users of the app to download it themselves, will actually constitute the act of "propagate a work". If you want to be on the save side you can just assume it does, if not you can contact a lawyer experienced in all the jurisdictions where you are distributing your code.

Answer 2

Yes. No. It depends.

You need to abide by the license of all libraries you use, including their respective dependencies.

If you look at permissively-licensed libraries (MIT, BSD, Apache,...) or the LGPL (whose copyleft license is limited to the library) this does not limit your choice of license of the main programme as long as you abide by the attribution requirements and possibly the requirement to allow replacement by a ABI-compatible library in case of the LGPL.

If you are linking to GPL-licensed libraries it can be argued that your programme itself is a derivative of these libraries and that you have to choose a GPL license yourself. Even if your legal advise disagrees on this point, and you choose for your source code a different license, you WILL have to distribute your compiled binaries which include the GPL libraries under a GPL license. Essentially this means you can distribute your source code under whatever license you choose AND HAVE TO distribute it also under GPL, at least for those versions you ship compiled binaries.

An authorative source? That is in the end only a court ruling which depends on the jurisdiction you seek advice for. However the FAQ, for instance, of the OSI is a good source, also the GPL FAQ.