Qt-interest Archive, February 2007
Re: How come KDELibs can use LGPL?
Message 1 in thread
On Wed, January 31, 2007 14:08, Karl Hiramoto wrote:
> Is that to say that if you make a commercial closed sourced application
> that runs on KDE with KDELibs then you have to buy a QT commercial
> license?
Yes.
> Is it a GPL loop hole?
No. This is intended.
If you build KDE-apps you have two choices:
KDELibs ==> LGPL (allows linking to commercial and free apps)
Qt ==> GPL (allows linking to anything that is GPL compatible - eg. GPL
itself, or LGPL, or the newer BSD license)
Or you go the commercial (ISV) route:
KDELibs ==> LGPL (allows linking to commercial and free apps)
Qt ==> commercial license (allows linking to anything that does not
require to also deliver the Qt source code)
Trolltech has given you the choice to be GPL compatible or commercial.
KDE has given you the chance to still make this choice while using KDELibs
by using LGPL(*).
(*)Actually KDELibs uses various other licenses too, but the LGPL is the
most restrictive one that is used.
Konrad
PS.: you cannot link statically to KDELibs, the LGPL requires that the
user can exchange the libs against other versions that are binary
compatible.
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Message 2 in thread
On Thu, Feb 01, 2007 at 11:57:00AM +0100, Konrad Rosenbaum wrote:
> On Wed, January 31, 2007 14:08, Karl Hiramoto wrote:
> > Is that to say that if you make a commercial closed sourced application
> > that runs on KDE with KDELibs then you have to buy a QT commercial
> > license?
>
> Yes.
>
> > Is it a GPL loop hole?
>
> No. This is intended.
>
> If you build KDE-apps you have two choices:
>
> KDELibs ==> LGPL (allows linking to commercial and free apps)
> Qt ==> GPL (allows linking to anything that is GPL compatible - eg. GPL
> itself, or LGPL, or the newer BSD license)
>
> Or you go the commercial (ISV) route:
>
> KDELibs ==> LGPL (allows linking to commercial and free apps)
> Qt ==> commercial license (allows linking to anything that does not
> require to also deliver the Qt source code)
>
>
> Trolltech has given you the choice to be GPL compatible or commercial.
>
> KDE has given you the chance to still make this choice while using KDELibs
> by using LGPL(*).
Something like the following table?
APP linked? QT KDE TT
========================================
Closed No N/A N/A None
Closed Yes No Yes(1) None(2)
Closed Yes Yes No Commercial
Closed Yes Yes Yes(1) Commercial
Free No N/A N/A None
Free Yes No Yes(1) None
Free Yes Yes No GPL or QPL
Free Yes Yes Yes(1) GPL or QPL
========================================
(1) Only if dynamically linked
(2)This is doubtful, probably commercial
where:
N/A = Not applicable
None = Not Required
Closed = proprietary/commercial/closed license
Free = GPL, LGPL, BSD, etc. FOSS license
Yes = true
No = false
App = Application software license
Linked? = Whether the app links with QT/KDE libraries
QT = Qt libraries
KDE = KDE libraries
TT = License required by TrollTech
For example, A closed application linked to Qt and KDE requires
a TT commercial license because KDE does not distro Qt sources.
>
> (*)Actually KDELibs uses various other licenses too, but the LGPL is the
> most restrictive one that is used.
>
>
>
> Konrad
>
> PS.: you cannot link statically to KDELibs, the LGPL requires that the
> user can exchange the libs against other versions that are binary
> compatible.
>
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>
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Message 3 in thread
Peter Gostelow schrieb:
> > ..
> Something like the following table?
Given the fact how often this question ("Can I use/[static|dynamic]
link/take source code of "Foo" which is licensed under "Bar" together
with "Hype" which is licensed under "Bubble"?) comes up and I have long
given up trying to understand all this lawyerish implications that arise
from such questions:
Maybe someone should come up with a simple application where you can
enter the above data and a simple "Yes" or "No" pops up :)
You could license this application under a "triple-license": GPL, L-GPL
and commercial, depending on your needs and the answer you're
expecting... *ouch* ;)
Cheers, Oliver
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Message 4 in thread
On Wed, Jan 31, 2007 at 02:17:13PM +0100, Karl Hiramoto wrote:
> Karl Hiramoto wrote:
> >Andreas Pakulat wrote:
> >>On 31.01.07 10:49:15, Gilles Debunne wrote:
> >>
> >>>Gabriel M. Beddingfield wrote:
> >>>
> >>>
> >>>>Qt is not embedded into KDE. KDE did not repackage Qt under a new
> >>>>license. KDE is an application that utilizes the Qt library (KDE
> >>>>libs links to the Qt libs). Since the FSF says that LGPL and GPL
> >>>>are compatible licenses, that means that you can distribute them
> >>>>together and link the programs together. Linking an LGPL program
> >>>>to a GPL program like this is OK according to the licenses, to the
> >>>>FSF, and to Trolltech.
> >>>>
> >>>But then, if one uses the resulting library, which license can be
> >>>used GPL, LGPL, both ?
> >>>
> >>>Consider this case: I take a cool GPL lib, I add some extra code
> >>>around it in order to create a new lib, that I release under the
> >>>LGPL. Then I use my modified lib as a black box in my commercial
> >>>application. Seems to break the GPL principles right ?
> >>>
Heh, the GPL principle is to eliminate proprietary software, not work
with it, so it tries to get you to ask this question:
How do I develop profitable (i.e. commercial) GPL software?
... and not ...
How do I profit from other peoples' GPL software for myself?
The following table should clarify the difference between commercial
and free software and the L/GPL licenses.
L/GPL vs Software
**********************************************
* License | software mix *
* | *
*Mix GPL LGPL | Cost Freedom*
*=======================+====================*
* 1 Yes Yes | No Yes *
* 2 No Yes | No No *
* 3 Yes Yes | Yes Yes *
* 4 No Yes | Yes No *
*============================================*
* Key: Cost=commercial, Freedom=free *
* Yes=allowed, no=prohibited *
**********************************************
Note in the above table the GPL applies to both commercial and non-commercial
software (where Cost is both Yes and No), but never to proprietary
(where Freedom is No).
Your case centres around these questions:
1- Does the GPL lib and your app require each other to build and run?
If yes, it violates the combined work clause. If no, you're ok.
2- Is the GPL lib distributed with your app as a combined work?
Answer same as 1-.
3- Will a LGPL license expand the GPL lib in the proprietary area?
If yes, use the LGPL, if not, don't.
One way I see it working, is like this:
1- Make a LGPL plugin for your app.
2- Make your plugin compile and work _without_ the GPL lib.
3- Make the plugin find and include the GPL lib, if present.
4- Build your app with your plugin only, _without_ the GPL lib.
5- Distribute your app + plugin + GPL lib.
Your mod'd lib cannot be used as a 'black-box' because it is a GPL
license with a relaxed 'comibined work' clause and the source must be
made available (white-box), even if you only distro the app binary.
The only black-box is the app code you write separately and distinct
from both the GPL lib and your LGPL wrapper. This means anyone can write
libs that match your wrapper API, and sell them (which adds value to your
app).
The difference between a 'combined work' and 'aggregation', is whether the
GPL lib _must_ be built with your app. If it isn't, it is merely
aggregated and ok. Whether your app _works_ without the GPL lib is
irrelevant (to the GPL).
But, of course, if you GPL your app, you can combine every L/GPL package
out there. The money is made in servicing customers who use your app, so
make it serviceable, not proprietary. Your competitors help you expand
your market when they distro your app and make it better :)
The crunch comes with TT requiring a 'commercial' license for Qt, which
raises the question whether you can GPL and sell KDE apps using Qt's
'Free Edition' libraries.
> >>
> >>Right that doesn't work. However you miss the point that one is
> >>perfeclty able to buy a commercial licnse for Qt and then link lgpl
> >>KDElibs against that and then build a commercial app on top of both.
> >>
> >>The important thing here is that Qt is both GPL and commercial (and
> >>there are differences between both versions).
... which confuses me because the GPL allows commercial use, while TT
seemingly hides this fact by calling their proprietary licence 'commercial'.
> >>
> >>Andreas
> >>
> >>
> >
> >Is that to say that if you make a commercial closed sourced
> >application that runs on KDE with KDELibs then you have to buy a QT
> >commercial license?
> >Is it a GPL loop hole?
> >
> It is not a loop hole. After googling i see:
>
> http://kdemyths.urbanlizard.com/myth/59
> http://developer.kde.org/documentation/books/kde-2.0-development/ch19.html
>
>
> **Myth
> You can't write closed source KDE applications because, while the KDE
> libraries are LGPLed, Qt is under the GPL.
>
> **Facts
>
> You can write closed source applications for KDE, if you aquire a Qt
> license from Trolltech to do so.
>
Do you still need a license if you don't distribute, such as a banking or
booking service? In other words, if you write a program others pay you to
use, but can never buy and install, does TT require a commercial license?
> While the GPL requires that all program that link against GPL'd code
> also be GPL'd, the LGPL makes no such restrictions.
>
> Therefore, the KDE libraries (which are LGPLed) do not restrict the
> licensing of code they are linked against. The limiting factor becomes
> Qt itself (commercial, GPL or QPL).
>
> If you develop using a commercially licensed Qt, you can distribute your
> KDE program under a commercial license of your choice.
Does this mean each user must also run the app with commerical QT libraries?
>
> If you develop using Qt Free Edition, your program must also be Free (it
> must be released under a license that is compatible with either the GPL
> or the QPLv2).
>
>
> --
>
> --
> Karl Hiramoto http://karl.hiramoto.org/
>
> --
> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx with
> "unsubscribe" in the subject or the body.
> List archive and information: http://lists.trolltech.com/qt-interest/
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