LGPLv2.1: Distributing dynamically linked executable without the LGPL library

Question

I am developing a proprietary (non-open source) commercial application that depends (both directly and indirectly through direct dependencies) on some LGPLv2.1+ libraries (specifically some MinGW64 libraries from MSYS2).

I have understood that if I distribute the libraries as binary DLLs, I must provide notice of the usage of the LGPL libraries and offer to provide source code for them. This is cumbersome, as I am not in fact in possession of the source code. I would have to download the MSYS2 build scripts and all related source code, and make sure that I can produce the same binaries with them.

If instead I write a script that downloads the binary packages from the MSYS2 repositories and tell the users of my software to run it, them I think that I am not distributing the libraries myself. Instead, I would distribute my dynamically linked executable, and the downloader script.

Having read section 5 of the LGPLv2.1, I am unsure whether the executable I want to distribute would count as a "work that uses the Library", and unsure how the other paragraphs of section 5 affect the situation.

Do I have to offer source code or mention the LGPL libraries? What other obligations from the LGPL am I left with?

Answer 1

If your executable requires the DLLs to be present when it is run, then your executable is a "work that uses the Library" as defined in section 5 of the LGPLv2.1. This is independent of whether the DLLs themselves are distributed together with your executable or not.

If you don't distribute the DLLs themselves, then your obligations are spelled out in section 6 of the LGPLv2.1.

You are required to mention your use of the DLLs, the fact that they are under the LGPLv2.1 license and you must include a copy of the license.

Depending on the target audience of your application, you could have an installer download the DLLs you need, or you can document that the user needs to install MSYS2 before they can use your application.