Assume we have a software which we developed completely ourselves from scratch. We are thinking of making the source code available to others, thus I am pondering what license to use.

My question is: would a GPL-like license covering above mentioned software (e.g., the European Union Public Licence) create an incentive to buy an exception? I read about "selling exceptions" here: https://www.gnu.org/philosophy/selling-exceptions.en.html , and here: Open-source license to prevent commercial use?.

For clarification: our software is a library that would be a building block for simulation software, so pretty much at the bottom of a software stack. We plan to sell exceptions to an open-source license, but the demand is probably not very high. I am looking for experience (not opinions) whether or not such a model would actually generate some revenue. Second-hand or hear-say experience is fine, though. Qt is one such example, but I am interested in more examples, especially in cases where there is no big foundation or company behind the OSS.

I have also perused the license comparisons at OSI and on this Wikipedia page. And I think, I understand the difference between commercial and proprietary software (at least in layman's terms).

  • 3
    Is it your intention to sell exceptions?
    – MadHatter
    Commented Apr 21, 2020 at 14:46
  • 3
    I'm not sure this question has an answer other than opinions on whether some commercial practise is good/bad/successful/hardly working Commented Apr 21, 2020 at 14:47
  • 1
    Thanks a lot. I have added "For clarification" in my question.
    – Gab
    Commented Apr 22, 2020 at 15:30

1 Answer 1


Copyleft terms like those in the GNU GPL place obligations on distribution of the software. Therefore, copyleft terms place an incentive to purchase an exception (i.e., a separate, non-copyleft license) only when the recipient expects to distribute the software further.

For example, Qt is a collection of UI components that are available under the GPL, so people who use Qt libraries in their own software must disclose their source code and license their software under the GPL as well. If someone doesn't want to do that, they can purchase a proprietary license from the Qt Company to allow distribution without source disclosure.

If the software you plan to distribute is a complete software product that recipients are unlikely to distribute further, then there is no incentive for them to purchase a license: they have the software, and they may keep it and run it without any obligations.

If your software is primarily used for running a network service, you might consider the AGPL, which also places copyleft source-sharing requirements whenever someone uses a modified version of your code to run a network service.

  • Thanks a lot. I have added "For clarification" in my question.
    – Gab
    Commented Apr 22, 2020 at 15:31

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