Cygwin GPL (Was: [rsync-announce] Graphical rsync!)

David Starks-Browning starksb at
Thu Mar 14 06:33:04 EST 2002

On Wednesday 13 Mar 02, David Bolen writes:
> David Starks-Browning [starksb at] writes:
> > Are you also distributing the source to cygwin1.dll?  It is illegal
> > not to.
> Well, if it's an unmodified version, I expect a simple pointer to the
> Cygwin site and/or CVS tree would be sufficient.  

No, because you don't know what version of the sources will be
available from other sites.

> Physical
> distribution is not necessarily the only way to satisfy the GPL, and
> if the included cygwin1.dll is simply a binary downloaded from the
> Cygwin site, then I think a reference to that site would satisfy
> clause 3c of the GPL.

(If I read it correctly...) You can only use 3c if you got binaries
according to 3b.  But Red Hat makes the source code available
directly, not with a "promise" to do so for 3 years.  So anyone who
redistributes also has to make the source code available.  Besides,
you can't rely on Red Hat to continue to provide sources for the
*exact version* of the DLL you're distributing for 3 years.  If they
don't, then *you* are in violation of the GPL.  The only "safe"
interpretation is to provide sources to cygwin1.dll along with the

For an example of how to do it right, see Robert Scholten's site at
<>.  Note
that you don't have to *force* users to download source to
cygwin1.dll, but you have to make it available.

Sorry to tire the rsync mailing list with such details.  But it does
come up here occasionally where people wish to distribute rsync.exe
with cygwin1.dll and nothing else.  I suspect Robert does it the way
he does now because Red Hat complained when he distributed binaries

Of course I'm not a legal authority, but I am familiar with Red Hat's
position because I monitor the cygwin mailing lists carefully.  This
comes up there occasionally, as you would expect.

Ask Red Hat if you don't believe me. :-)

(Cygwin FAQ maintainer)

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