Restrictions in license

Brian Behlendorf brian at
Sun Sep 25 19:49:44 UTC 2005

On Sun, 25 Sep 2005, Ian Lance Taylor wrote:
> Brian Behlendorf <brian at> writes:
>> P.S. - why doesn't the qmail license qualify as an Open Source license
>> given clause #4?  That license restricts my ability to distribute
>> qmail in modified form - but doesn't prevent me from distributing
>> patches.  The license "explicitly permit"s distributing builds, see
>> the bottom of:
>> but these derived works have to behave exactly the same.  So what kind
>> of license was #4 designed to allow?
> As I recall, OSD #4 was written to permit the QPL which only permitted
> source code modifications to be distributed in the form of patchsets
> to the original distribution.

I don't know if QPL projects show this, but the only-patchset nature of 
the qmail mods out there shows this is a lousy thing in the long-term if 
the original author becomes disinterested but doesn't hand it off... 
thereby not quite fulfilling the "right to fork" that I for one feel is 
the essence of open source.

> As you say, my understanding has always been that qmail doesn't
> qualify as open source because it does not permit the distribution of
> modified binaries.  You can distribute modified source code, but you
> can't distribute binaries built from the modified source code.  That
> would seem to violate OSD #3.

Yes, you can distribute binaries built from modified source code - but it 
still has to "behave exactly", which moots the point of most useful 
modifications.  Still, it doesn't forbid all modifications.


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