On Mon, Jan 10, 2011 at 7:01 PM, Noufal Ibrahim <nou...@gmail.com> wrote:
> > I could be totally wrong about this. I'm not a lawyer but this is my > general understanding of why dual licensing exists. > > On Mon, Jan 10 2011, Narendra Sisodiya wrote: > > [...] > > > That's exactly I want to understand. Let take a fictitious example I > > purchased a book on PyQt. I wrote an excellent close software which is > > based on PyQt. > > To use a third party package, you will need to accept their license - be > it the GPL, a BSD type (non-copyleft) license or a more restrictive > EULA. > > If you're using PyQt, you are bound by whatever license the version > you're using it released under. > > If you are using the libre version of PyQt, it is made usable to you > under the terms of the GNU GPL (I haven't checked the website myself but > that's what this thread suggests). > > The GNU GPL is a copyleft license which insists that applications > derived[1] from software licensed under it also be released using the > same licensing terms as itself. This is a hack (one of RMSs best in my > opnion) using copyright to make sure that the software "stays" > free. It's not possible to take a GPL program and make a non-free version > of it (which is possible with non-copyleft free-software licenses like > the MIT license). > > It's generally agreed upon that linking your code with a library > constitues a dervied work (I don't know if this has been legally > tested). This means that your program if released under a non-free > licenses is in violation of the GNU GPL and so you're doing something > illegal. Some libraries are released under the LGPL which is the GPL > with an extra clause that says that linking against them doesn't > constitute a derived work. AFAIK, PyQt is not one of them. > > > I am start selling this proprietary software in market. > > Selling has nothing to with software being libre or not. You can sell > copies of GPLed code (like RMS himself did with early copies of Emacs). > > > people started purchasing this software from my website. > > Fair enough. > > > They download PyQT. and they run my close software. > > Your program *requires* PyQt to run so you have to obtain it under a > license. If you obtain a GPLed version, you have to make your own > application free software to confirm to the GPL. If you want to keep > your code closed, you have to obtain a version of PyQt that lets you do > this (for which you'll have to pay). > > This is the point of dual licensing. > > Another example is the GNU readline library. You cannot make a closed > source application that uses it without violating the GPL. If you want > to do that, you'll have to contact the copyright owners (the FSF), ask > them to give it to you under a different license that allows this for > which they might charge you money. > > [...] > > > Footnotes: > [1] The is the term where much of the legalities hide - if I use a > GPL'ed library is my code "derived"? If I use code that's generated by a > GPL program, is my code "derived"? etc. > > Thanks !! -- ┌─────────────────────────┐ │ Narendra Sisodiya │ http://narendrasisodiya.com └─────────────────────────┘ _______________________________________________ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
