Licensing question LGPL
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It would be really, really nice if Digia could provide us with some "this is what you can and cannot do with Qt under LGPL" scenarios as this question keeps cropping up and, to date, I am yet to see fully definitive and satisfactory answers.
I am aware that law always involves insane amounts of ambiguity open to "legal interpretation" (how else would lawyers make their money?) but I am sure they can cover the most common use cases?
Does anyone know who to approach with such a request or do you think one should just forward an email to Digia's general contact?
I would think some sort of "petition" will probably have the best chance of success.
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How do you suppose Digia should do that, given the sheer number of jurisdictions in the world? Copyright laws, on which (L)GPL is based, is not the same in every country. That makes it hugely complex to get to one single statement that will absolutely hold true everywhere.
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[quote author="goblincoding" date="1359544338"]It would be really, really nice if Digia could provide us with some "this is what you can and cannot do with Qt under LGPL" scenarios as this question keeps cropping up and, to date, I am yet to see fully definitive and satisfactory answers.[/quote]
Well, ever since the Qt creators decided to release their work under the LGPL, you can use it under the terms of the LGPL, and that's it. Leaving the quibbles out (i.e. assuming the LGPL is interpreted as it was intended), it means that linking an unmodified LGPL'ed library (DLL or SO file) against a proprietary program file is allowed. Redistributing LGPL'ed library files is allowed anyway. If Qt creators had not intended that, they simply would have chosen the GPL rather than the LGPL. The latter exists exactly for the purpose of allowing proprietary software to use the library - which would not be possible with the GPL. And, as a matter of fact, there are tons of commercial/proprietary/ClosedSource software products out there that use LGPL'ed libraries...
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Be aware that macros, inlining or templates may create a derivative work, even though you dynamically link against the LGPL-covered code, which will force you to publish code as given in Section 6 of the LGPL.
This is the reason Qt comes with an "exception":http://qt.gitorious.org/qt/qtbase/blobs/stable/LGPL_EXCEPTION.txt to the LGPL.
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[quote author="Andre" date="1359544898"]How do you suppose Digia should do that, given the sheer number of jurisdictions in the world? Copyright laws, on which (L)GPL is based, is not the same in every country. That makes it hugely complex to get to one single statement that will absolutely hold true everywhere.[/quote]
I would just like to receive input from an actual lawyer as opposed to opinions and interpretations from other developers. My interpretation has always been the same as that explained by MuldeR above (thanks for laying it out that well by the way).
Yet if you are right and the LGPL's legal interpretation is based on the specific copyright laws of whichever country you are in then, at least theoretically, the possibility of completely disregarding the limitations imposed on the users of libraries by the LGPL is possible...which would kind of defeat the purpose...
(please understand that I am not looking for an argument here, I am just trying to explain why I think it will be nice to get some clarity from actual lawyers...that I do not have to pay :D)
If it is truly impossible to receive such definitive input, then I think I will stick to the interpretation shared with MuldeR and just hope I don't ever become an edge case studied in Copyleft 101 at <insert university of choice here>.
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[quote author="Lukas Geyer" date="1359548111"]Be aware that macros, inlining or templates may create a derivative work, even though you dynamically link against the LGPL-covered code, which will force you to publish code as given in Section 6 of the LGPL.
This is the reason Qt comes with an "exception":http://qt.gitorious.org/qt/qtbase/blobs/stable/LGPL_EXCEPTION.txt to the LGPL.
[/quote]
Well, im supriesed this has lead to (yet another) discussion^^
thx for the link to that exception, i read about it in an old post, but that linked to a nokia page, which i think did not exist anymore.
I guess i will follow the common interpretation then, to link dynamically, provide the Qt Librarys and all that stuff.
I think i understood that excpetion right, when i say that it means you can use templates, macros and inline functions without having to make that part of your personal (non library) code open source.
I guess i migth check if i can find something abaout derivative work in the german copyrigth law, but otherwise i will follow the common interpretation.
as i said im not planning to write huge software and sell it for hundreds/thousands of euros, but small neat tools and programms publish them for free and just place an ad or so to pay the webspace or the coffee :P i don't really think somone would be nitpicking when i fullfill 99.9% of the license but miss one small small point.
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Yes, the exception basically says that the use of Qt headers, macros, inlined code and template is permitted and will not trigger the LGPL restrictions (which might be the case without this exception).
I am, however, in practice with Mulder. These are just nuances of the LGPL, and you should be able to safely use Qt under the terms of the LGPL as long as you link dynamically and comply with the redistribution rules.
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[quote author="goblincoding" date="1359556472"]
I would just like to receive input from an actual lawyer as opposed to opinions and interpretations from other developers. [/quote]Tough luck, I highly doubt the forum is swarming with lawyers, eager to engage themselves with giving away legal advices for free.
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well at least here in germany lawyers are not insured when giving legal advide on an open plattform like a forum. So when they give wrong advice and get sued they have quite a huge problem.(i'm not even sure if they are allowed to give legal advice in a forum at all)
so nearly every law board you find here is run by amateurs.
there are some blogs run by lawyers but ofc they don't give special advice there, just general stuff.
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[quote author="utcenter" date="1359568639"]Tough luck, I highly doubt the forum is swarming with lawyers, eager to engage themselves with giving away legal advices for free.[/quote]
Which is exactly why I initially wondered if it would perhaps be possible to "engage Digia for help":http://qt-project.org/forums/viewthread/24340/#112427 ;)
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Digia is not a legal outfit, legal advisory as I said is not cheap and most certainly something that one would just give away out of charity. Digia can solve all your legal woes by selling you a commercial license. Or perhaps "with this video":http://www.youtube.com/watch?v=5HWBaHAvjoo.
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I just wondered: is sth. like this( http://qt-project.org/wiki/Make-a-QLabel-Clickable) where you add a new class which inherits from a Qt class considered a change in Qt that has to be layed open source? you do that all the tme at least for the main winowd, but here you add functionality to a Qt object.
e: as i somehow can't answer: thanks a lot
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No. It does not modify Qt code.
