View Full Version : Qt 4.5 to be released under LGPL

14th January 2009, 07:59
Qt Software just announced that Qt v4.5 and above would now *also* be available under the LGPL license (in addition to the existing GPL and commercial licenses.) They are even going to offer support for the LGPL version.

They are not making this retroactive. If you have Qt 3.x or Qt <=4.4, you only have a GPL or commercial option.

The official press release is here (http://www.qtsoftware.com/about/news/lgpl-license-option-added-to-qt):

ICS has released a whitepaper on the Implications of the LGPL for commercial
developers here (http://www.ics.com/files/docs/Qt_LGPL.pdf).

We have no longer have the best toolkit that is also the most expensive for commercial development!

Sorry.... RIP: GTK+ wxWidgets and the rest of the bunch


14th January 2009, 08:08
Bad form to reply to your own email... My apologies

But checkout the video (http://www.qtsoftware.com/about/licensing) that Qt Software published.


14th January 2009, 08:18
Can't watch the video from here ... but doesn't LGPL mean that Qt can now be used for commercial development without purchasing a license? Therefore no one would pay anymore (except the solutions) and the users who already paid are getting angry?

The trolls already answered my questions ;)


14th January 2009, 08:29
Youtube blocked at your site?

LGPL does mean that commercial users can use Qt (v4.5+) without purchasing a license. But there are some limited restrictions and other reasons to continue using a commercial license. There are more details in the whitepaper I linked to in the first posting.

Qt has been available for some time under the GPL license. So this is kind of a new option for people. Are people going to be disappointed because they might have been able to wait for the LGPL option, perhaps. But it is sort of like buying that new computer and then a few months later hearing about the quad processor upgrade... Life changes.


15th January 2009, 08:13
Ok, dumb question:
Will they allow Visual Studio integration for 'everyone' then?

15th January 2009, 14:30
probably not. Qt Software is still part of a business and while some of its products are open sourced and available for free (all Qt editions and the tools that go with it) there are things left to sell : support, VS integration, more extended license (that allow static linking or even embedding of Qt code into proprietary app instead of dynamic linking)...

15th January 2009, 20:36
Probably the LGPL version will be identical to the GPL one, it will probably even be the same bundle - they will only add another licence option to choose from when accepting the licence during configuration process.

15th January 2009, 21:37
There is an interesting discussion going on at Pro-Linux.de (http://www.pro-linux.de/news/2009/13677.html) (sorry, German only) under the topic "Kein Unterschied zur GPL?" LGPL 2.1 has a clause that might prevent any benefits the LGPL could have. The problem seems to arise when inline functions, macros or templates are used, which definitively applies to Qt.

This seems to be a general problem with C++ and the LGPL, so I expect the Trolls are aware of this? Still, I would be glad to see some official statement concerning this issue. Does anyone know more on this?

15th January 2009, 21:40
I think the same issue concerns using code generators such as uic, moc, lupdate and lrelease and probably also qmake but I'm sure the "problem" will be resolved by the time LGPL enters the picture.

15th January 2009, 22:17
I think there is a difference between those code generators, as Qt Software as the authors of these generators can specify what license the generated code is under, and the LGPL clause. The point seems to be that code licensed under LGPL can, in certain circumstances, be included in application code, which would render the whole application code LGPL. The exceptions made by other C++ libraries aren't made without any reason! And the LGPLv3 has some clarifications concerning this topic, which I doubt would be made if there wasn't some problem.

To me, that discussion sounds a lot like paranoia, but there might be a problem if Qt Software didn't take any precautions against that way of interpreting the license. I trust in Qt Software to have considered that interpretation, but I just wanted to point this issue out, as it seems to evoke a pretty heated discussion. And if, by any chance, this might have slipped Qt Software, I hope they know about this by now ;)

15th January 2009, 22:23
The macro "problem" also exists under C, yet no one has ever complained about it except in regards to C++. But no matter, Trolltech will be adding an exception covering this. It will be safe for you to use QList!

15th January 2009, 22:58
I am not afraid of using any part of Qt covered by a LGPL license, I just wanted to point out that discussion to you. And hopefully to Qt Software, too, as they are mainly affected by this discussion, too. I am definitively sure that Qt Software will handle any of these questions!

The point whether anyone has complained about it or not is irrelevant, as this can become a licensing issue anytime.

Licensing can be quite a complicated issue

16th January 2009, 08:55
Let's not be paranoid :)

16th January 2009, 12:53
Don't worry, they are aware of the issue and the legal are working out the correct exception note for templates/inlines as they have blogged about on qt labs.

16th January 2009, 20:06
Licensing can be quite a complicated issue

Only if you let it!

For some reason programmers like to decompile legal documents down to a ridiculous level. Not only are they missing the forest for the trees, they're missing the tree for the leaves!

16th January 2009, 20:20
they're missing the tree for the leaves!

Or maybe the leaves for the bugs sitting on them ;)

What is most important LGPL means new programmers using Qt which in turn means more benefits for people already experienced and at the same time means new users, applications and frameworks based on Qt, which means better quality of the product and more functionality (which again is for our benefit).

Hopefully it will also mean bigger QtCentre community ;)

16th January 2009, 21:07
For some reason programmers like to decompile legal documents down to a ridiculous level.

You can never be too thorough with legal documents. There might just be a lawyer waiting for you not to be ;) And the "problem" with LGPL 2.1 is quite valid, as can be seen by the fact that it is addressed in LGPL 3 and will be addressed by the Trolls.

Besides, with the abundance of licenses out there you'd better know what you are doing when using some third-party code. Sometimes I get the feeling that every company releasing something as OSS creates it's own license ;) Fortunately, only a few of them are used by the vast majority of projects.

16th January 2009, 21:59
Will they allow Visual Studio integration for 'everyone' then?

As Thiago stated in a blog comment (http://labs.trolltech.com/blogs/2009/01/14/nokia-to-license-qt-under-lgpl/), the VS Integration plugin will remain to be commercial-only for the time being.

16th January 2009, 23:06
You can never be too thorough with legal documents. There might just be a lawyer waiting for you not to be

Do you really think a developers' forum is the place to go to get legal advice? Don't listen to what other developers are saying, get yourself a lawyer. Other developers' lawyers don't count, it needs to be your own. Until then, stop spreading the fear, uncertainty and doubt.

17th January 2009, 13:15
I never asked for legal advice, I just wanted to point out an issue that came up in every discussion on the license change I have read so far.

17th January 2009, 14:33
You know I've read on one website's forum. People are still complaining about the LGPL. They want Qt to be BSD, MIT or whatever. Some people are never grateful for anything. I don't see why it should be BSD, MIT. What? They want to make a fork of it? Like the people over at wxWidgets wanting a wxQt o_O. Kinda retarded.

But hey look at it this way too. More people that move to Qt will probably find this site and join so more business for us ^_^

17th January 2009, 16:23
If they want to fork, they can do that with the GPL or LGPL edition as well as it was the case with Qt/Win and Qt3.

17th January 2009, 17:48
They basically just want the "do what the fuck you want" kinda license. No copyright left backs etc

17th January 2009, 21:17
There is nothing to stop them. They can start a new project, work on it and release in under DWTFYW licence. If it becomes better than Qt, that's fine.