python and gpl

Scott Robinson dscottr at
Mon Jan 31 21:12:29 CET 2005

On 30 Jan 2005 21:59:25 -0800, Paul Rubin
<> wrote:

>John Hunter <jdhunter at> writes:
>> The question is: does shipping a backend which imports a module that
>> links with GPL code make some or all of the library GPL.
>Literally speaking, no, not automatically, any more than driving a car
>makes you into a licensed driver if you weren't one already.  But if
>you weren't licensed, then you've broken the law by driving the car.
>So your question should be: 1) is shipping that backend one of the
>things you need the GPL to license you to legally do, and 2) if so,
>does the GPL in fact give you that license?
>If you're asking in terms of legal enforcement, the answer is 1) maybe
>and 2) almost certainly not.  I think it's better to ask in terms of
>the GPL's spirit.  I would say that it's not in the GPL's spirit and
>that GPL die-hards would consider that use objectionable, though they
>might make exceptions for specific cases (so it doesn't hurt to ask).
>Some authors who use the GPL are less strict about how they interpret
>it, so again, the friendly thing to do is ask the author.
>  * If a backend module somebackend does
>     import somelib
>    where somelib is a python wrapper of GPL code, is somebackend GPLd?
>It's GPL'd if you GPL it.  If you don't GPL it, then distributing it
>it may be a GPL violation that could get you taken to court.  I
>believe the FSF's view is that it is fact a violation; however, the
>courts have not yet established this.  The law doesn't have a
>black-and-white boundary.  It's more like a fractal.  The only way to
>find out what a court will decide is to actually try a case there.
>Rather than try to probe how closely you can dance around the
>boundaries of the GPL, you might just ask the author of the GPL'd
>library whether what you want to do is ok with him or her.  If s/he
>says no and you do it anyway, you're both inviting trouble over the
>possible infringement, and also inviting people to try to use your
>code in ways you don't like.  Since the free software movement depends
>on a spirit of cooperation, I think it's best to avoid trying to press
>too hard against the boundaries of anyone's licenses.

If you read the GPL, it claims everything it can (any "work" created
using GPLed "work").  My guess is that anything that calls the code in
a way not specifically allowed by the author is going to get you into
trouble.  IANAL, but from what I can remember about earlier licensing
issues, any code specific for a GPLed library (especially "import")
will get you into to trouble.  Having a non-free library with an
identical API and issuing 
	exec("import "+sys.argv[1])
where the user can supply sys.argv as the name of the gpl'ed library
will work (I think there is a free/non-free library out there that is
never run, but exists for exactly this condition).

Scott Robinson

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