The same old topic: Licensing.
-
Hi,
I need to prepare a lecture for my colleagues about Qt Development, and one of the topics is licensing. But it's a very controversial topic, since the three Qt licenses make its licensing hard to understand. I tried to read "Qt Licensing(Qt Licensing)":http://qt.nokia.com/products/licensing) a few times, but I'm still confused.
So, I'll start with a some questions:
-
Can I develop and deploy closed-sourced commercial applications without buying a commercial license of Qt?
-
A more specific question, since the answer may be different: can I develop and deploy closed-sourced commercial applications without buying a commercial license of Qt, distributing it with the original Qt libraries, without any changes on it?
My personal projects are free and open sourced, but I need these questions answered so I could convince (or not...) some coworkers to use Qt on their commercial projects.
-
-
[quote author="ucomesdag" date="1275403434"]To my understanding you must also make the source code available.[/quote]
Which source code?
-
Not a lawyer too, but AFAIK you can distribute your closed-source commercial software with or without original Qt libraries if you use LGPL. And you con't need to provide source code by this license.
AFAIR there are some issues with static linking with Qt libraries. -
You do not need to distribute the application source code (ref. LGPL section 6) as long as the application is only dynamically linked to Qt (which is the ordinary case). Then the LGPL allows you to distribute your application under "the terms of your choice" (i.e. any license you like), provided that those terms "permit modification of the work [i.e., your application] for the customer's on use and reverse engineering for debugging such modifications."
If you modify Qt itself, then you must distribute the source code of your modified version of Qt if you want to distribute an application that uses it. You still do not have to distribute the source code of your application.
(Standard disclaimer: this is not official Nokia legal advice blah blah blah)
-
[quote author="aavit" date="1275465885"]"permit modification of the work [i.e., your application] for the customer's on use and reverse engineering for debugging such modifications."[/quote]
To what extent is this required, do you just not sue them when they hack your app, or provide the ability to write plugins, or prpovide debug libraries (basically as good as source code, isn't it?)
This is very interesting, I love Qt personally... But I always thought the licencing thing would stop me producing closed source apps or commercial programs...
-
[quote author="jorjpimm" date="1275466723"] To what extent is this required, do you just not sue them when they hack your app, or provide the ability to write plugins, or prpovide debug libraries (basically as good as source code, isn't it?)[/quote]
As I read it, the LGPL in this regard only places restrictions on the terms of the (optionally commercial, closed-source) license that you choose to distribute your application under. In effect, the LGPL says that that license may not contain things like "modifications or reverse-engineering is not allowed".
The FSF may provide more in-depth on this: http://www.fsf.org/licensing/
[quote author="jorjpimm" date="1275466723"] This is very interesting, I love Qt personally... But I always thought the licencing thing would stop me producing closed source apps or commercial programs...[/quote]
While that might have been an issue earlier, while Qt was under Trolltech's business model, it should not be now, after Nokia started releasing Qt under LGPL also (which happened about a year ago).
(Standard disclaimer applies)
-
Have a look at this blog post for information about this directly from Qt legal:
"http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/(http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/)":http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
-
[quote author="MariusG" date="1275501216"]Have a look at this blog post for information about this directly from Qt legal:
"http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/(http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/)":http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
[/quote]Has that page changed recently? Because I'm sure I have been on a page with the same title, and it used to be not so useful, but now looks very good.
-
[quote author="MariusG" date="1275501216"]Have a look at this blog post for information about this directly from Qt legal:
"http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/(http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/)":http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
[/quote]Thanks that made it all clear to me!
-
Since comments at
http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
are closed, I was wondering if I could have an answer at the following scenario/question:
If someone writes a closed-source Qt application for Windows based on the LGPL-licenced Qt framework, and if he/she doesn't change the libraries, and if he/she linked dynamically with the dlls (Qt for Windows) then:
a) if he/she doesn't provide the dlls but he/she only provides the exe
b) if he/she provides both the exe and the dllsdoes he/she has to provide the (unchanged) source code of the dlls?
-
Stavros Filippidis, AFAIK in both cases you shouldn't provide code.
-
@_Denis Kormalev_: Just to clarify, I am NOT referring to the source code of the application, but to the source code of the Qt libraries (QtCore4.dll, QtGui4.dll, etc). In any case, I am not a lawyer, I am just have these questioned unanswered. :)
-
[quote author="Stavros Filippidis" date="1276707919"]@_Denis Kormalev_: Just to clarify, I am NOT referring to the source code of the application, but to the source code of the Qt libraries (QtCore4.dll, QtGui4.dll, etc). In any case, I am not a lawyer, I am just have these questioned unanswered. :)[/quote]
Yeah, I understood that question is about Qt sources. Anyway when you use Qt with LGPL license you need to provide link to Qt. And everybody who wants can take sources from Qt website.
-
@Alexandra: In my opinion, it would be interesting if you would consider re-opening comments at
http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
so that someone from Qt/Nokia's legal department could clarify additional questions that we could post there. ;)