On 05/06/2009 07:50 AM, William Stein wrote: > On Tue, May 5, 2009 at 3:25 PM, Brian Granger <ellisonbg....@gmail.com> wrote: >> Hi, >> >> I have a question about Sage and the GPL. Here is the main question.. >> >> IF I write code in a Sage notebook, AND I redistribute the code, do I >> need to release my code under the GPL? >> >> Here is a bit of background... >> >> At a conference in the last year, one of the Sage developers was asked >> this question, and their answer was... >> >> "You can do whatever you want with your code, you don't have to >> release it under the GPL" >> >> In general, I don't think this answer can be right, but I think it is >> actually a bit subtle. Here are some of the issues that I see (all of >> this assumes that I do want to distribute my code to others)... >> >> * Is the code pure python or does it use the sage syntax? If the code >> uses the sage syntax, I think it must be released under the GPL. >> * Does the code being written actually use any GPL libraries (like the >> sage python package)? If the code uses GPL libraries, I again think >> it must be GPL'd.
> Publicly distributed code using GPL'd library must be GPL'd. Suppose Ondrej's program ------- from sage.all import x print x**2 ------- were a bit longer to actually contain some creativity (but no line from any GPL source code). Suppose he puts that in a file aaa.sage and distributes that (without sage). Why should there be any restriction on this source? He may, of course put that under BSD (it's open source anyway). The file itself does not "use" Sage. It's simply a string of characters. Only if somebody downloads Sage, downloads aaa.sage and actually runs aaa.sage, the sage library is used. But then distribution has already happened and there is no obligation for Ondrej to change the license of aaa.sage from BSD to GPL. >> * If a sage notebook is "source code" does clicking "Share" in the >> notebook constitute "distribution". In other words, if a bunch of >> people start sharing sage notebooks, do they all have to be GPL? > No. This is internal distribution, so the GPL doesn't apply. This is > no different than the NSA (say) distributing a program from one > researcher to another, and obviously they don't have to GPL their > code. No. But for a different reason. The notebook is a separate piece. If you don't distribute it together with Sage, then it's only a string of characters (and as such not particularly useful) and I don't see a reason why such distribution must be under GPL rules. If, however, you choose to distribute your notebook together with Sage then it can be considered an extension/derivative work of Sage and as such the whole thing (=Sage+notebook) has to be GPL. The important term is "distribution". Of course, also NSA-internal distribution of a GPL program has to follow GPL rules. Suppose I write a program and *distribute* it to my wife under the GPL. If my wife chooses to *distribute* that program to my child, she can do that, but she must follow the GPL rules. Now three people have that program (and source code) and none of us is forced by GPL rules to publish the source code to anybody else in the world if no further distribution happens. Only if you distribute the work, you must follow GPL rules. >> The usage case I have in mind is using this to teach University >> courses in computational physics. I know others are already doing >> this (William is right now I think). If I share notebooks with >> students and they with me, does everything have to be GPL? > No, definitely not. But if you post the notebooks publicly and they make use > of the sage library, then they have to be GPL'd. I'd say if you distribute the notebooks alone without any GPL'ed software, then you are free to choose any license you like. >> This is relevant, because I need to >> clarify these issues for students and faculty who would use Sage in >> this manner. It isn't necessarily bad if the answer is "GPL", but we >> all need to know this. > You might consider consulting with a lawyer at your university. > Universities sometimes have > lawyers for this sort of thing. Yes, that is always a good thing. There are, for example, certain items of GPL2 that don't apply in certain countries. Don't get me wrong here. I am a fan of GPL. And if everyone distributed his software under GPL there would not be such a lot of wasted mailing-list hours that discuss license issues. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
