Re: [Help-gsl] Using gsl algorithms

[David Zaslavsky]

Licensing issues are complicated, even within a single country's laws.
But from what I've heard (and this comes with the standard disclaimer
that I'm not a lawyer, this is not legal advice, etc.), I believe the
following statements are reasonably sound at least under US law:

- The GSL does implement a lot of fairly standard algorithms, which were
published in books and papers before being implemented in GSL. The fact
that you also implement these algorithms does not itself make your code
a derivative work of GSL. For example, simply including a Monte Carlo
integrator doesn't make your code a derivative work.

- On the other hand, if you copy the specific way in which the GSL
implements some algorithm, I believe that does make your code a
derivative work. It doesn't have to be a verbatim copy of source code to
constitute copyright infringement.

- If a court were called upon to determine whether your code was copied
from the GSL code, I think there would be some subjectivity involved,
depending on just how close your code is to the GSL code, and also
taking into account how much variability is possible in the
implementation of the algorithm. (As you said, quicksort is pretty
standard, so it's probably harder to make a case of copyright
infringement based on similar-looking quicksorts than based on
similar-looking MC integrators.)

- If you have never looked at the GSL source code, then I doubt anything
you write would turn out similar enough to be considered to be copied
from GSL. (However, linking with GSL does make the resulting program a
derivative work of GSL.)

- If you're going to put your code under the GPL anyway, I would say
it's probably not worth the time and money to figure out officially
whether you would really be required to do so. ;-)

There's a lot of good information about this at the GPL FAQ page: v3
 http://www.gnu.org/licenses/gpl-faq.html
and v2:
 http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html

:) David

On 09/30/2013 11:36 AM, Tucker DiNapoli wrote:
> This question is mostly out of intellectual curiosity more than actual
> necessity. I'm writing a software library for the julia programming library
> and I'm basing many of my algorithms off of the gsl. I'm wondering what
> this means in terms of licensing, while I do intend to license my library
> under the gpl I would like to know if this is actually necessary. Does
> copying algorithms, or basing new code off of preexisting code fall under
> the same rules as actually copying or using that code or is it different.
> I'm sure that to an extent this is a bit of a legal grey area (for instance
> no one could accuse you of copying code if you write a quicksort that looks
> like theirs) , again this is really just for curiosity's sake more than
> anything else (being as I do actually need to link with the gsl for my
> library anyway so I'd need to make my code gsl regardless).
>   Tucker DiNapoli
>

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