Is it legal to package the Cygwin installer executable — and some of its corresponding packages — and run it from another installer that installs a proprietary and commercially sold application?

The commercial application's source does not "build with" or "link to" any source code from any of the Cygwin source nor any of its packages' source. However, after the commercial application installs and is run, users can invoke some binaries that the Cygwin installer places onto the user's machine — namely bash.exe, mintty.exe, and tail.exe. Cygwin's licensing page claims that "Most of the tools are covered by the GNU GPL, some are public domain, and others have a X11 style license." I realize that distributors of binaries under the GNU GPL are required to include access to the source code for those binaries — which makes complete sense. However, does this mean that the entirety of the source code for the proprietary commercial application must also be distributed? My take is that no, it is not required, since the commercial application is deemed "a separate program" according to this statement in the GNU FAQ.

Can anybody shed some light on this situation?

  • 1
    The word commercial is bogus. GPL is commercial. But not proprietary. Commented Feb 22, 2018 at 23:58
  • opensource.stackexchange.com/q/6556/1084 is near identical question Commented Feb 23, 2018 at 0:00
  • opensource.stackexchange.com/q/6548/1084 is near identical question Commented Feb 23, 2018 at 0:01
  • I don't understand your comment, and the question you linked to does not have an answer either. I'm looking for a "yes or no" answer to my question, or even something in between, but I'm not sure how your comments help me.
    – ariestav
    Commented Feb 23, 2018 at 4:52
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    “Free software” does not mean “noncommercial”. A free program must be available for commercial use, commercial development, and commercial distribution. Commercial development of free software is no longer unusual; such free commercial software is very important. You may have paid money to get copies of free software, or you may have obtained copies at no charge. But regardless of how you got your copies, you always have the freedom to copy and change the software, even to sell copies. — extract from gnu.org/philosophy/free-sw.en.html Commented Feb 23, 2018 at 10:01

1 Answer 1


We need to look in the Free Software definition and or the Open Source definition.

The Free Software definition is easier to understand. So in most cases I would start there. Sadly I could not see anything obvious in it. I think it is there but not as obvious at this from the Open Source definition.

  1. License Must Not Restrict Other Software

The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be open-source software.

As far as I know, everyone agrees that if some software is Open Source (according to the definition) then it is also Free Software (according to the definition), and vice versa. However there may be some disagreement an which licences are approved by each organisation.

  • Thank you for pointing me to this resource! Based on point (9) I think you are suggesting that it is permissible to do what I am asking. Since our application's installer starts Cygwin's installer as a sub-process which places binaries of Cygwin's base packages onto the user's machine, and our software only invokes those binaries, then it seems like iit's a go. We are double checking with an appropriate attorney, but thank you for your answer.
    – ariestav
    Commented Feb 23, 2018 at 15:28

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