[BangPypers] Suggestion for GUI

Narendra Sisodiya narendra at narendrasisodiya.com
Mon Jan 10 16:52:53 CET 2011

On Mon, Jan 10, 2011 at 7:01 PM, Noufal Ibrahim <noufal at 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
> 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

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