Cygwin license

DJ Delorie
Wed Mar 31 19:45:00 GMT 1999

OK, massive legal arguments (from both sides) aside, it is Cygnus's
intent that any programs that are linked with libcygwin.a must be
distributed under the terms of the GPL.

RMS's opinion on DLLs (and shared libraries in Unix) is that the mere
fact that they exist in a separate file does not in itself make them a
separate program in the eyes of the GPL (which has itself been subject
to lengthy legal review).  Since the two (your exe and cygwin's dll)
are inseparable for the purpose of running your program, they are
legally (according to the GPL) considered *one* program.  This means
that the GPL on the dll *does* apply to programs that require it.

If your program can operate *without* a cygwin dll available, then I
would probably agree that the libcygwin.a code *may* fall into that
"interoperability" regime (although, at the moment, any program that
uses libcygwin.a usually does so in such a way that it will not
operate without cygwin1.dll) if they avoid anything in libccrt0,
libcmain, getopt, dll_entry, or dll_main, which aren't in the dll at
all (the remainder of the objects are dll thunks, which can easily be
regenerated from cygwin1.dll itself with microsoft tools).

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