I have a backup application written in Delphi. Now I want to add Delta capability by using RDiff.exe + cygwin1.dll.

cygwin1.dll is covered under the GNU GPL License . Does this imply that I have to give my entire Delphi application as Open Source ?

  • Do you distribute this application or just use it for your own personal needs? Commented Feb 4, 2017 at 18:20
  • 3
    What exactly does the phrase "Clubbing my Exe" mean? Commented Feb 5, 2017 at 1:00

3 Answers 3


If you just call RDiff.exe as a separate process, without linking your program against any GPL components, you do not need to put your program under GPL. You can see RDiff.exe as a plugin to your program and apply this section of the GPL FAQ.

Note that cygwin1.dll is under the LGPL License, not under GPL, only RDiff is under GPL (but I assume you want to distribute both).


This is really a question for a lawyer but if you are redistributing the GPLv2 components unchanged and with both the correct attribution and the licence of to those parts then you should be OK as long as you are simply interfacing to the code rather than embedding it. Note that your documentation should also include details of where to get the source code of the GPLv2 components.

Be sure to only utilise the public API of those items as private API details a) may change & b) may make your work a "derivative work" in which case you would also have to GPL your code.

Do please check with a lawyer, or if you are working for a company with their software licencing specialist, before going too far with this. For example I know of one company that has guidelines that state that for redistribution, even as an external, unmodified, component they are unlikely to approve any licence that is not "Apache or better" which excludes both GPL and LGPL.

N.B. I am not a lawyer in any way shape or form.


You are incorrect in your assertion that cygwin1.dll is licensed under the GPL. See this description of the license terms on Cygwin's web site. Specifically, the license of this DLL is LGPL, not GPL, and it has an additional exception which reads:

As a special exception, the copyright holders of the Cygwin library grant you additional permission to link libcygwin.a, crt0.o, and gcrt0.o with independent modules to produce an executable, and to convey the resulting executable under terms of your choice, without any need to comply with the conditions of LGPLv3 section 4. An independent module is a module which is not itself based on the Cygwin library.

This means that for your use, you have no need to worry about licensing conditions on Cygwin, even were you to directly link to cygwin1.dll yourself.

  • That was my first reaction when I read the question, too, but then I thought the OP was only be a little bit sloppy in his wording. It seems he wants to distribute RDiff.exe + cygwin1.dll, so since RDiff.exe is under GPL, the core problem remains.
    – Doc Brown
    Commented Feb 5, 2017 at 14:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.