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Old 01-27-2005, 11:47 PM   #1
uman
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Simple question about the GPL


I wanted to use Qt/Windows/Free to make an application, however it is licensed under the GPL. Does this mean that I would also have to license my program under the GPL?

I am so totally not a lawyer, forgive my stupidity.
 
Old 01-28-2005, 01:38 AM   #2
jlliagre
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According to the QT site, there's no free or GPL'd version of QT for Windows:
http://www.trolltech.com/developer/f...tml?cid=20#q17
 
Old 01-28-2005, 08:12 AM   #3
uman
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Yes there is, but it isn't maintained by Trolltech. Can someone please answer my question?
 
Old 01-28-2005, 01:47 PM   #4
student04
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Quote:
Originally posted by uman
Yes there is, but it isn't maintained by Trolltech. Can someone please answer my question?
To answer your question:
If a piece of code, program, etc is published under the GPL, and you wish to modify it then you must provide your source code AND put the new software under the SAME GPL version, unless otherwise specified. You may sell and redistribute anything under the GPL, just that you must be cautious about third party applications in, for example, distributions such as RedHat. When you change their source code, they say that you must remove all "RedHat" logos, etc because it is no longer RedHat.

About the GPL QT:
How can you be sure of this when you haven't provided any proof?
 
Old 01-28-2005, 02:55 PM   #5
Dark_Helmet
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student04 is right, to an extent. I'll try to clarify. If you take someone else's software (licensed under the GPL), you modify it and intend to distribute it, then you must license the code under the GPL and you must also be willing to provide the source code. The GPL doesn't state that you must include the source code when you distribute, but if you don't, then you have to provide it if it's requested. Most people find it easier to just include the source and be done with it. Also, if you don't distribute the program, then none of these licensing issues come into play.

The above applies if you're tinkering with a full-fledged application. If, however, you're writing a brand new application, and linking against GPL licensed libraries, it's different. Actually, most "GPL libraries" are in fact licensed under the LGPL. Essentially, the LGPL allows anyone to use/link the library for any purpose (proprietary, closed source, or open). So you can develop a completely closed source application that relies on nothing but LGPL'ed libraries, and be completely OK. You just can't do anything "special" with the libraries.

However, I would strongly recommend at least reading over the license(s) that cover the libraries you intend to use. The classic expression "ignorance is no excuse in the eyes of the law" most definitely applies. And my usual disclaimer: I'm giving you my interpretation/understanding of the licenses; a judge's interpretation may differ vastly. Even if you're not a lawyer, it won't hurt to scan over the licenses a few times... especially if they offer differring styles of license.

Last edited by Dark_Helmet; 01-28-2005 at 02:57 PM.
 
Old 01-28-2005, 03:29 PM   #6
jlliagre
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Quote:
Yes there is, but it isn't maintained by Trolltech. Can someone please answer my question?
Well, I did answered your question providing a link to the original authors of QT stating you looked misled.
However, without your help, I found there's a port of qt based on GPL (no LGPL) sources on http://kde-cygwin.sourceforge.net/qt...2/features.php that claims having no issues with QT and I suppose it is the one you're talking about.
So, assuming they really do not breach QT license, you are as previously stated forced by the license to make your own developments GPL'd and open source.
You can avoid it by purchasing a commercial license to Trolltech, which could help them supporting their business model.
 
  


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