A few comments based on having thought carefully about this for a few years now.
1. The preamble of the GNU Free Documentation License (GFDL) from the Free Software Foundation (home of the GPL) says: "The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others." It would be shocking if this was somehow incompatible with GPL'ed software. I view a mathematics textbook, including Sage code, to very much be documentation for Sage in a very real sense - how to use Sage to learn and do mathematics, and vice versa. And I think the spirit of this license is consistent with the open philosophy embraced by Sage. 2. The GFDL is extremely explicit about what you can, and cannot do, and especially is clear about "Opaque" copies (think PDF) and "Transparent" copies (think LaTeX-as-ASCII files). The GFDL allows you to make sections as "invariant", which I have used on Prefaces, but some then consider the usage to not be truly open. I no longer use invariant sections, so you can modify my Preface if you choose. ;-) http://linear.ups.edu/preface-2.00.pdf 3. In contrast, the various CC licenses are quite short, I believe in an attempt to be understandable. 4. Many textbook authors use the CC NonCommercial (NC) clause on their books. My guess is that they do not want to see a traditional publisher profit from their work. However, if an open text can be placed on a print-on-demand site (like Lulu.com, or Amazon's CreateSpace, or others), in some cases then sold at production cost, one can always undercut a traditional publisher with a quality physical product. Any increase in price needs to be accompanied by some extra value (better manufacturing, distribution, availability). If I could wave a magic wand, I'd ban CC-NC on all textbooks. ;-) 5. My linear algebra textbook runs to about 900 pages (embarrassing yes, but it has everything a student would want, including full solutions to many problems). PDFs are about 7 MB, but the jsMath version compresses to 695K, so if distributed as compressed worksheets we should be able to achieve similar sizes. 6. I build graphics from source, as part of a commitment to make the *whole* book open source. I was using PyX, which now appears to be a dead project, and will this spring shift to something like Asymptote or MetaPost. As it is, the diagrams produced by PyX are PDFs at about 6K each, so the sizes of graphics can be mitigated as well in some ways. 7. As noted, CC does not require source, perhaps because some media (music, video, photos) don't have such a thing. Would we distibute Sage just as binaries? <opinion> I have used CC on various things I have written, like an essay for EDUCAUSE about open textbooks and video of presentations. It stikes me as appropriate for something like the Sage wiki. However, I don't think I would ever use it on a large project, like a textbook I have spent several years on. It just stikes me as too loose about the responsibilities placed on the next person to modify or distribute your work. In contrast the GFDL is very explicit, and like the GPL, places certain (reasonable) conditions on anyone who both modifies and distributes your work, while giving everyone the right to use (read, copy) your work, and to distribute it unmodified. My hope for Sage is that we find it possible to eventually include a reasonable selection of quality (ie reviewed, vetted) textbooks that mesh nicely with Sage itself, and that we encourage licenses that are in the best interests of both authors, teachers and readers. </opinion> Thanks for everybody's contributions to this thread. It does seem to take a while to wrap your head around the idea of a world where publishing houses are not the only players in the academic textbook market. Rob -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
