About Trolltech QT OpenSource license.

Paul Boddie paul at boddie.org.uk
Wed Apr 11 12:59:22 CEST 2007


On 11 Apr, 11:51, "king kikapu" <aboudou... at panafonet.gr> wrote:
>
> Ok, i see...So i can use Qt OS edition and earn money from this as
> long as i explicitly say (is a reference to a GPL in a readme text
> file enough for this ?) that this software is under the GPL lisence
> and i have the obligation to give the source code with it.

I'll leave the specifics of this case to one side and say that for any
software that you intend to distribute under the GPL, you should
provide references to the licence at least in some kind of text file
(I use COPYING.txt for this), but also in your source files (I
typically use module docstrings, but I imagine that comment lines
might be better in some respects), as well as a copy of the licence (I
use LICENCE.txt for this). You should find the licence text in any GPL-
licensed package as well as at the FSF site:

http://www.fsf.org/licensing/licenses/gpl.html

The "making money" aspect can be simplified to this: you can sell
copies of your software, but anyone receiving that software is
entitled to the sources "at cost", and since they receive the software
under the GPL, they are entitled to redistribute it under the same
terms. One popular misunderstanding is that if a company is selling
GPL-licensed software, they have to give the sources away to anyone
who asks; in fact, only people who have received the software are
entitled to the sources:

http://www.fsf.org/licensing/licenses/gpl-faq.html#CanIDemandACopy

Various companies do, however, give away sources to anyone but then
make money out of the effort to turn such sources into executable
systems. For example, Red Hat make the sources on which their products
are based available to anyone, but since the effort in building them,
putting everything together, testing the result, and so on is non-
trivial, people pay them money to do that particular work.

As has been said elsewhere in this discussion, the specific use of the
term "commercial" in the case described may be aimed at a corporate
mindset which equates "commercial" to "proprietary", but Free (and
open source) Software can be the basis for commercial activities, too.

Paul




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