LGPL license clarification

Question

I would like to request some clarifications about the LGPL license. Specifically, I am interested in understanding how it works in the context of selling (for a fee) software that must comply with the LGPL license.

Based on my understanding (please correct me if I am wrong): When I sell my software, I must also include the source code. The client who purchases my software is free to modify it as they wish. My questions are as follows:

Can a client who purchases my software redistribute it freely, including for free? Can any individual request access to my source code without having to pay anything? If one of my employees, who develops LGPL software, moves to a different company, do they retain any rights over the software they wrote, or does it remain the property of my company until it is sold? I would also like to present a specific case:

I have a client commissioning software and, by contract, requiring that I deliver the software along with source code and its intellectual property rights. I intend to use QT (the free version), which imposes compliance with the LGPL license.

Given that I must provide both the intellectual property and the source code to the client regardless, does the LGPL impose any additional obligations on me?
Will only the client who pays for the software have rights to it?
Do I have any obligations towards the open-source community or anyone who does not purchase the software?

Answer 1

First and most importantly: the LGPL is designed for libraries, and is designed to limit your source-sharing copyleft obligations to only the LGPL library itself (and any library-specific changes you may have made). In contrast, the GPL (rather than the LGPL) is much stricter, requiring copyleft obligations on the entire project, even if the GPL component is used as a library.

In answering your questions, I'll assume you're distributing a library that's a direct modification of an LGPL library. If you're actually distributing complete runnable software, then your obligations are mostly limited to passing on the source of the LGPL library, not your whole project.

Will only the client who pays for the software have rights to it?

This is correct, copyleft source obligations trigger on distribution, and only to recipients of the binary code.

Will only the client who pays for the software have rights to it?

Can a client who purchases my software redistribute it freely, including for free?

Yes to both: only the client has rights, initially, but one right the client now has is to share the software in an unlimited way, either for free or for a fee, provided they also share the source of the library under the LGPL. If that happens, many more people could quickly have rights to your library. If the client has an interest in not sharing the software (e.g. because it gives their competitors a similar advantage), then they might choose not to exercise this freedom.

Can any individual request access to my source code without having to pay anything?

Do I have any obligations towards the open-source community or anyone who does not purchase the software?

No. If someone doesn't have a copy of your software, you can't be legally compelled to give them a copy of the binary or source code if you don't want to share it. However, they could get a copy from someone else who is willing to share or sell it.

If one of my employees, who develops LGPL software, moves to a different company, do they retain any rights over the software they wrote, or does it remain the property of my company until it is sold?

Generally, employees are not considered recipients of (L)GPL software given to them by their corporate employer -- legally, they operate as the same "legal person" as the corporation person. Furthermore, the (L)GPLv3 (but not v2) allows the transfer of copies without (L)GPL rights when the transfer is done to a contractor solely for the purpose of making improvements to the software

However, if the employee ever received a copy of the software outside their responsibilities as an author (e.g., they bought a copy, or someone else published it or gave them a copy), then they would become a recipient under that transaction.