Calling GPL code from a Python application

Terry Hancock hancock at anansispaceworks.com
Wed Jan 4 06:51:57 CET 2006


On Tue, 03 Jan 2006 20:48:12 -0500
Mike Meyer <mwm at mired.org> wrote:
> If you want to know the intent of the authors, that is
> that libraries covered by the GPL would infect programs
> they are linked with, whether it's dynamically or
> statically. The Library (now Lesser) GPL was created to to
> allow programs to be linked with LGPL'ed libraries without
> infecting the program. If the library in question was
> released under the LGPL, the authors of the GPL say you
> can use it. Otherwise, they say not. But see the above
> paragraphs about judges, copyright holders and lawyers.

I have to say that in my conversations with developers, the
choice of the LGPL for Python libraries is only a matter of
signalling intent to library-users.  All the ones
I've talked to seemed to think that the GPL allows dynamic
linking anyway, but they wanted to avoid any question about
it. Some other authors go ahead and use the GPL but provide
a notice of their interpretation along with the package.

As I read the GPL itself (but I am not a lawyer), it cannot
possibly restrict you from doing this (because your code
does not include a copy of the GPL'd work), and it
explicitly allows you to distribute the GPL'd library with
your application (provided you provide source code and keep
it separated in obvious ways from your own code -- such as
putting it in a separate archive file, etc). That's the
"mere aggregation" clause that allows that.

However, it is true that the FSF is unhappy with this
loophole and would like to pretend it isn't there, so those
warning you that you could get sued are probably right. I
just think that you would be in the right in such a case and
should win.

It is interesting to note that the FSF holds the position
that the language that "gives you this right" *doesn't* --
it just clarifies the fact that you already hold that right,
because it is provided by "fair use".  Their position is
that it is not possible to restrict the *use* of software
you have legally acquired, because copyright only controls
copying.

In order to take away that right (according to the FSF
theory expressed in the preamble of the GPL), you must have
a *contract*, not merely a *license*. Generally if no
consideration was paid (it was zero-cost), and nothing was
signed, there can be no such contract.  This is in conflict
with the "click-through" EULA theory, which the FSF denies
is legally binding.  Thus their own arguments contradict
their desire to control your use of the software.

Mind you, I'm not necessarily rooting for either side of
this -- I'm just interpreting what I've read. The GPL is
a fascinating read, BTW, and it isn't particularly long. ;-)

Cheers,
Terry

-- 
Terry Hancock (hancock at AnansiSpaceworks.com)
Anansi Spaceworks http://www.AnansiSpaceworks.com




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