Qt 4.5 to be released under LGPL

[mhatch]

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.

Mark

[ksqt]

Ok, dumb question:
Will they allow Visual Studio integration for 'everyone' then?

[fullmetalcoder]

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)...

[wysota]

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.

[rexi]

There is an interesting discussion going on at Pro-Linux.de (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?

[wysota]

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.

[rexi]

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

[Brandybuck]

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!

[rexi]

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

[wysota]

Let's not be paranoid

[seneca]

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.

[Brandybuck]

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!

[wysota]

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

[rexi]

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.

[Brandybuck]

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.

[rexi]

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.

[rexi]

Will they allow Visual Studio integration for 'everyone' then?

As Thiago stated in a blog comment, the VS Integration plugin will remain to be commercial-only for the time being.