On 05/06/2009 07:44 PM, Robert Bradshaw wrote: > On May 6, 2009, at 10:37 AM, Tim Lahey wrote: >> Doesn't both Maple and Mathematica make use of GMP? I thought they >> did. >> >> They aren't licensed under the GPL. > > GMP is LGPL, not GPL. If what Ralf said were correct (which it > isn't), there would be no need for an LGPL at all.
Could you point me exactly to the place where I am wrong? Suppose you have a library A that is distributed under license L. If you write a program B that uses the library A *and* you create a binary and distribute the binary for B then that contains A (I don't care whether that is static or dynamic linking). Let's agree that B without the library A is the extension E (which is purely new code). If you distribute B=A+E and want to keep the sources for E private then you cannot do this if L=GPL, but you can if L=LGPL. This settles the need for LGPL. However, I did not describe this case. Even if L=GPL, you can distribute a form of E in a non-source form (which is probably useless without A) under any license you like. You might have produced that form of E without even having any GPL software on your computer. So why would somebody have the right to force you to distribute E under GPL? What if A was formerly under BSD and then changed to GPL? Would that mean you suddenly can no longer distribute E under a closed license. Why? If you don't distribute A you don't distribute GPL code and thus have no obligation. Now if a person P takes your E and also gets A and in some way produces a binary B, then P has no right to distribute B if L=GPL, since this would require him to distribute B under GPL as well, but without the sources for E this is clearly impossible. But of course, it is no problem to use B for private things. Now think of A as being Sage and E as being a notebook. Ralf --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
