PySimpleGUI, a GUI framework for Python, has previously been published under the LGPLv3. They just announced that they are changing to a subscription model with PysimpleGUI 5, and that previous versions will be sunsetted.

Their new license is also pretty unclear about how open source software using their library is supposed to work. Furthermore, it's unclear if a free and open source Python program using PySimpleGUI would be considered hobbyist (free) or commercial (paid subscription).

But since all prior versions were distributed under the LGPL, I don't understand how this works. Isn't the prior version still FOSS? Furthermore, wouldn't the new version also be somehow subject to LGPL since it presumably is mostly the old code that is LGPL licenced?

Lastly, the new licence also has a statement about not distributing prior versions of PySimpleGUI, which also didn't quite make sense to me:

Licensee may not (and shall not permit any third party to): ... (i) incorporate PySimpleGUI or any portion thereof into any software that purports to subject it to open source software or similar license terms, including any prior version of PySimpleGUI (modified or unmodified) which was previously distributed under such licenses;


1 Answer 1


Isn't the prior version still FOSS?

Licences do not inhere in software, but instead their obligations attach to the recipient through the act of conveyance. If you received a copy of this software under LGPL, your rights and obligations with respect to that copy remain those described in the LGPL. We cover that in much more depth in this question.

Furthermore, wouldn't the new version also be somehow subject to LGPL since it presumably is mostly the old code that is LGPL licenced?

Given the consent of all existing rightsholders, both new versions of the software and new copies of old versions may in future be conveyed under different licences. This can occur either through explicit agreement of existing rightsholders, or because the project required a CLA from contributors that gave the project the right to do this (consent to relicensing thus already having been given).

So if you didn't happen to get yourself a copy of the existing sources under LGPL, now might be a good time to find someone who did, and get a copy off them, under the terms of LGPL.

  • 12
    Everything you used to be able to do with copies that were distributed under LGPL you may still do with a copy you have received under LGPL.
    – MadHatter
    Feb 14 at 5:56
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    If you really like the software (the software, not the company - it's important not to mix these up) and you want to continue its FOSS heritage, consider getting together with other like-minded people and forking the last available LGPL version under a new name. Your team will pick up the maintenance burden, but if done right, people will choose your fork rather than the commercial venture.
    – Keiji
    Feb 14 at 7:55
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    One thing one cannot do is to call a fork of the LGPL3 version of "PySimpleGUI" by the name "PySimpleGUI". That name is trademarked. You'll need a new name. Feb 14 at 13:24
  • 2
    @Barmar I am not a lawyer. Blatantly violating a trademark name is not a question that requires lawyerly skills. Whether coming "this close" to violating a trademark name may require lawyerly skills, and IANAL. Feb 14 at 15:43
  • 3
    Could we not have that discussion in this comments field? It's arguably not even on-topic for this site, though it might be well-received over at law.SE.
    – MadHatter
    Feb 15 at 8:18

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