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GPL Apps linked to Qt/Windows
by Richard Stellingwerff on Monday 12/Apr/2004, @14:46
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"You cannot take a GPL Linux program, compile them with Qt for windows and give the executable to somebody else, because you would violate the GPL. [Ed: because Qt on windows is closed source]"
I don't really understand this. GPL applications are allowed to link to closed source libraries, as long as it does not have a dependency on them, right? How else could things like cygwin exist? Or GIMP for non-free Operating Systems. What about GPL'ed JAVA apps. JAVA surely ain't opensource.
I think this is just plain nonsense. Any GPL app should be possible to be released using a commercial Qt DLL, as long as the *application* itself has the source code available.
Am I wrong? If so, please explain to me why. |
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Re: GPL Apps linked to Qt/Windows
by Evan "JabberWokky" E. on Monday 12/Apr/2004, @15:24
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The program would have a dependancy on it. The key part is the "and give the executable to somebody else". You have to provide source to build that app under the GPL... including all dependancies and licensing dependancies.
Now, if you count Qt as a system library (there is a specific clause in the GPL about those), you can do it. But would you say that Qt is a system library?
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Re: GPL Apps linked to Qt/Windows
by Richard Stellingwerff on Monday 12/Apr/2004, @23:53
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Maybe Qt is not a System Library, although it is used by many apps on my system. The app would not have an excplicit dependency on it either. It could just as well be compiled with Qt/X11 for Windows. So why is it a problem if I chose to compile (and release) it with my own non-free library.
What defines a system library anyway? Is Java for windows a system library? And it's not GPL, is it? How come GPL'ed JAVA apps exist then. Are they violating the GPL?
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Re: GPL Apps linked to Qt/Windows
by Anon on Tuesday 13/Apr/2004, @09:38
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If you give away the binary it will either be linked to Qt/Win32 or to Qt/X11. The latter is not a problem because the two licenses are not incompatible. The former is a problem because the license on Qt/Win32 restricts you from meeting your obligations under the GPL. You will have infringed on one or the other copyright depending on which action you take.
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Re: GPL Apps linked to Qt/Windows
by Evan "JabberWokky" E. on Tuesday 13/Apr/2004, @11:07
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The GPL defines it in the following paragraph:
The source code for a work means the preferred form of the work for
making modifications to it. For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable. However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.
I don't think Qt is "normally distributed" with the "major components" of Windows. Thus it is not a system library and does not fall under the special exception.
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Re: GPL Apps linked to Qt/Windows
by Toojays on Tuesday 13/Apr/2004, @05:54
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The crux of what you are saying is that the result of merely linking to a library should not create a derived work of that library. Without going into the legalities of the GPL, I would point out that this goes against the spirit of Free Software. Even just the freedom to study the source code to see how it works is kind of meaningless if part of "how the program works" is tied up in a non-Free library. Now the GPL has a special execption for non-Free operating system components, because back when it was written we didn't really have a Free operating system. (Who knows whether the next version of the GPL will have that exception? What about GPLv4?)
Another point to consider is that GPL does not just enable to you access the source code, but allows for further distribution. For instance, I can download a version of LyX which is linked against Qt non-commercial 2.3. If this is really licensed under the GPL, then I should be able to put it on a CD and sell it for real money. However, if I did that, I would not be able to fulfil section 3 of the GPL, _and_ I would be using non-commercial Qt for commercial purposes. Surely I am not free to do this. So here you have a piece of software which has had its freedom reduced by linking against a non-free library.
I hope this helps you understand why they couldn't do this, if not I am happy to continue the discussion.
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