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I want to use QtWebKit, which uses QtCore and QtGui DLLs. Can I sell a library which uses them and redistribute them with my library's instalation? The library is not open source.
Qt is under the LGPL version 2.1, so, yes, you can sell a library and distribute the Qt library with it, provided that when you distribute your library, you "give prominent notice with each copy" that Qt is used and that Qt is covered by the LGPL.
This same rule applies to both applications and libraries that use Qt, as long as they are not derivative works, and if you do make any changes within Qt's code that those changes are published under the terms of the LGPL.
Licensing information for QTWebKit can be found at http://doc.qt.nokia.com/4.7-snapshot/qtwebkit.html#license-information.
Agree question s/b closed - this isn't the right place for legal advice.
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I'm looking at a Qt Extended application built circa 2006-2008 and upgrading to a newer Qt framework. What direction(s) are recommended to upgrade / rewrite this application to get on the latest supported version of some Qt framework?
I assume this is an embedded platform, and in this is case first of all you need to get Linux BSP with newer Qt version (you can look into Buildroot or Yocto or even a distribution like Debian, all of these have excellent support for Qt), and make sure that you have full HW supported for your platform. This is pretty much platform and product dependent, so i can't really be more specific.
After you got the OS up and running, you can start to port your application to port to Qt5. This can be pretty straightforward (see for example https://wiki.qt.io/Transition_from_Qt_4.x_to_Qt5), but can be rather complicated if a lot of Qt Extended related features were used. Again, this depends a lot on the application itself, so hard to give guidelines.
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I'm about to publish a free software written with Qt 4.8 GUI, can I publish the stand-alone version with dlls such as QtCore? Do I have to publish my code also?
If possible, could you make some examples of using GPL license legally?
Thanks very much!
If you want to publish your software using GPL then you have to provide the source code no matter is it free or you charge money for it. In GPL "Free" doesn't mean cost free but freedom to change the code etc.
In your case if you don't wish to give away your source code, then you you should use LGPL license. Qt is available under LGPL license too. The only restriction it puts is that you cannot statically link with Qt libs. You ought to use dlls as you are using. And if you only use Qt dlls then you can even charge money for your application.
http://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License#Differences_from_the_GPL
You can use LGPL library in your commercial, closed source, non-free/free application provided you link to the LGPL library dynamically (using .dlls, .so etc.).
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I'm a Delphi developer I only used to develop application on Windows platform only.
From now on, I wish to develop a GUI based database applications which target Windows, Ubuntu, OSX.
I don't have much knowledge about cross platform solution, I know I little about Java, I know almost nothing about Python and Qt.
Anyway, I prefer to use Python as the programming language and use Qt for GUI, my question is I'm not quite sure about...
What development tool and version (prefer latest if possible) do I need to install on my development machine which is running Ubuntu 13.04?
What are major differences between PyQt, Qt Designer?
Did you read basic Qt documentation?
You should write platform independed code to make it portable ;). Do not use OS-specific features, use Qt classes. You need a compiler for each platform. You need a Qt for each platform.
Visit qt-project.org and get latest versions. (And a lot of other information about Qt)
PyQt - is port of Qt libraries to python. Qt Designer - is software (tool) for making .ui files. Others??
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We are wondering if someone has experience with the way Qt license works. We want to develop a closed source, proprietary license application (with static linking to Qt libraries), which will be installed to several computers (> 100). We might consider purchasing a commercial license, but we are not sure whether the license fee is:
per developer
per workstation
per company
per installation
per team
anything else?
Anyone has experience in this area?
When I used it, eons ago, the license was "per developer".
This has changed now, as far as I can tell. Take a look at this:
QT commercial vs. non-commercial license for beginner and
https://stackoverflow.com/questions/2945612/qt-lgpl-licencing-for-a-free-application-with-closed-source
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I want to start a cross-platform project. I had my researches and now I am almost certain Qt is the right deal. There is a big obstacle here though: licensing.
I want to sell my project and I also don't want to give out any source related to my work or pay for a license. I checked and noticed Qt offers both commercial and open source solutions. I have heard too many conflicting sayings on Qt licensing which confused me a lot. Some say that even if I use LGPL version of Qt, I still need to submit my code. Is this true?
Can someone give me a simple explanation on Qt licenses and tell me if I can sell my application without any kind of restrictions at all or not? Would anyone tell me any other equivalents to Qt for cross-platform development without any restrictions?
Just dynamically link to Qt. If you dynamically link to LGPL libraries, there's nothing to worry about.
If you statically link to them, you can just distribute your object files (not your source code), and you'll be fine.
The idea of the LGPL is that the end user has to be able to replace the LGPL library with a version they want. Dynamically linking to the LGPL library lets you do that, as does statically linking and distributing your object files. So long as you do this, you can sell your closed source program all you want.
Of course, there's more to the LGPL than just this, but that's the relevant part.