Nothing to add on the legality of dynamically linking GPL code, but in the specific case of pyFFTW, please be aware that the conda-forge packages for this use STATIC linking of FFTW.  Static linking was chosen in order to get around a potential error for certain transform types when combined with MKL-based numpy.  See details at:

On Sun, Nov 5, 2017 at 2:37 AM, Juan Nunez-Iglesias <> wrote:
Ok here’s my suggested course of action, inspired in part by the movie The Life of David Gale:

1) Apply for a grant to fund steps 2-5.
2) Make a BSD-licensed library that imports fftw
2b) (optional) sell the library for $500/license.
3) Convince the makers of FFTW to sue. We would pay all legal costs from (1)
4) Put *most* of the funds from (1) towards the defense legal costs, though.
5) Win the lawsuit, thereby creating the required legal precedent and providing a massive boost to the BSD-licensed SciPy ecosystem.

Any takers? ;)


On 2 Nov 2017, 6:51 PM +1100, Stefan van der Walt <>, wrote:
On Thu, Nov 2, 2017, at 00:26, Nathaniel Smith wrote:
The FSF is definitely guilty of oversimplifying this, but it's
probably best to think of their position as a simple bright-line rule
of thumb, like... if you follow this rule you're definitely safe, and
if you don't follow this rule... well, it's complicated and ultimately
it might depend on what the jury had for lunch that day, so good luck.
Or at least you should ask an actual lawyer :-)

Should we not also ask: if we got sued, would an argument along the
lines of "yes, I know you've explicitly stated publicly that you meant
*this* with your license, but we prefer interpreting it like *that*"
fly? I have no idea how courts interpret these things, but if a
reasonable expectation was set, I can't see how ignoring it would
benefit us.

Until there's absolute clarity, or a confirmation from the authors or
the FSF that importing FFTW is OK, I wouldn't go there.

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