Em Qua, 2009-05-06 às 00:29 -0700, William Stein escreveu: > On Tue, May 5, 2009 at 11:57 PM, Robert Bradshaw > <rober...@math.washington.edu> wrote: > > What about > > publishing (collections of) worksheets under the CC license? Code > > snippets in books? Are your books GPL compatible? (Maybe you could > > claim fair use.) > > > > I have no trouble licensing code under the GPL, but I do think this > > places an onerous and inappropriate burden on all *users* of Sage, > > and the GPL is supposed to be about modifying/distributing code. >
including yourself. > Building software on top of GPL'd libraries like Sage *does* have > serious implications toward sharing. That's sort of the point of the > GPL'd. There's no sense in hiding that. > > Suppose you spend three years implementing an algorithm as part of > Sage to compute X (say some Monsky-Washnitzer cohomology > computations). Then somebody else writes and publishes a clever paper > that includes a several-page Sage program that uses your > implementation of X (plus many other things in Sage) to compute Y (say > p-adic Regulators of Jacobians of genus 2 curves). Would you > definitely be allowed to use their new code and include it in Sage? > > I think the GPL was designed to ensure that computer programs that > build on your programs must be shared under compatible conditions. > This has the pro that it means that your work is protected in that > when people build on it, they can't "hoard" their improvements. It > has the drawback that it puts an onerous (and inappropriate?) burden > on those same people, that when they on your GPL'd work, they can't > hoard their improvements. > > In one sense at least, Sage can never be an alternative to > Maple/Mathematica/Matlab/Magma, etc. With the Ma's, if one wrote a > big program on top of them, and wanted to distribute the program as a > complete self-contained closed source program (say something like a > standalone Mathematica demonstration), at least it would be > technically and legally possible. One would have to do some sort of > contract with say Wolfram, Inc., but that's quite reasonable. With > Sage that would be impossible, since the copyright is spread over > hundreds of people (some dead). Scipy/Numpy/Enthought's stack > does provide this extra feature, which Sage never will. > > There's a little good and a little bad in everything. > > William Here's something that may really upset you (specially since earlier you asked about which developers could be infringing the GPL, if one thinks about the most restrictive interpretation). You wrote a book last year. It does include code that should be executed in Sage. However, you haven't released the book under the GPL and instead signed with a publisher to distribute your book. OK, you did take some measures to ensure the book will be freely available to the public after some time, however the GPL does not include text to deal with that. So, if you really want to take the strict interpretation, you should make available your book right now, which would of course break your contract with your publisher. So, what could you do now? Could other developers sue you to make you release your book under the GPL? If other people published books which included Sage example code, could you sue them to release their books under the GPL? Now, if one mathematician happens to solve one of the Millenium Prize Problems ( http://en.wikipedia.org/wiki/Millennium_Prize_Problems ) in Sage. Would his proof be GPL? Would other proofs that depend on that also be GPL? What about the result itself? I guess this would pretty much restrict much of Mathematics itself, contrary to the "spirit of mathematics". Just my 2 cents with a truckload of salt. Ronan PS: Just to mention, if I had to choose I would release my libraries as LGPL, which would avoid much of the problems of both sides, or use some sort of dual-licensing, or even just not release them, but that's too extreme. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
