Use of GPLed Python extension modules

Bengt Richter bokr at
Sat Nov 22 22:33:15 CET 2003

On 22 Nov 2003 12:14:03 -0800, Paul Rubin <> wrote:

>rkern at (Robert Kern) writes:
>> Note that the question is phrased as a "proprietary vs. GPL"
>> dichotomy. I think the following entry is more appropriate:
>No I don't think it's more appropriate.  That entry is about adding
>your own module to a GPL'd program.  Such a module doesn't have to be
>GPL'd, as long as its license is "GPL-compatible".  The original
>question was not about that.  It was about using part of a GPL'd
>program in another program.  That is prohibited unless the second
>program is also GPL'd.

Yes, but even that wasn't the actual question the way I read it. To requote
[with my annotation]:
If a compiled Python extension module B includes code from some other 
software A which is licensed only under the GPL [resulting in B_GPLd_because_of_A],
do other Python programmes, C,  which import [this is the key relationship -- importing
a GPL'd module, irrespective of how it became GLP'd] module B also need to be licensed
under a GPL-compatible  license (assuming C is/are to be distributed to third parties)? 

The question ISTM is whether importing a GPL'd module is enough to trigger GPL obligations
on the part of the importing module. ISTM that is more like a program-program relationship
than incorporation of code (unless it modifies the source. e.g., with an execfile and changes
based on source knowledge). I.e., if a non-GPL module could be substituted without changing
the importer, IWT that would mean plug-compatibility rather than incorporation. But IANAL.
I haven't read the license recently, but I thought there there was some arms-length uses of GPL
software by proprietary software that are allowed, or am I mistaken? I don't know how long the arm
has to be though.

Bengt Richter

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