Use of GPLed Python extension modules

Robert Kern rkern at
Sun Nov 23 01:42:18 CET 2003

In article <7xislcjh4k.fsf at>,
	Paul Rubin <> writes:
> 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.

I think the same principles apply in both the OP's question and the FAQ answer.
Note that the FAQ answer mixes things up a bit in the following sentence: "But
you can give additional permission for the use of your code. You can, if you
wish, release your *program* under a license which is more lax than the GPL but
compatible with the GPL" [emphasis added]. I think the actual answer tries to
answer both the literal question in the FAQ and the OP's question.

If I have an application ("C") that uses the readline module ("B"), and I wish
to distribute it, I must distribute it under the GPL. Under my interpretation of
the FAQ answer, I can also give the recipients of the application more rights to
*my* code (the parts that are C and not B) such that they can, say, use a
routine that has no relationship to B (for example, a computational routine that
doesn't have a UI and therefore doesn't use readline at all) in a
GPL-incompatible project. I don't think that the GPL makes the distinction
between putting a GPLed module into a GPL-compatible program and putting a
GPL-compatible module into a GPLed program.


>From RMS

IANAL, and of course, RMS INAL, either, but until there's a court case examining
this issue in particular, I think we're safe.

Robert Kern
rkern at

"In the fields of hell where the grass grows high
 Are the graves of dreams allowed to die."
  -- Richard Harter

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