Qt licensing questions

Scott Wheeler wheeler at kde.org
Sat Jun 7 21:44:58 BST 2003

Hash: SHA1

On Saturday 07 June 2003 21:43, Alexander Neundorf wrote:
> Hi,
> it seems the mailing list kde-licensing at kde.org doesn't exist anymore 
> (http://mail.kde.org/mailman/listinfo/kde-licensing), so I don't know better 
> than posting it here.
> Well, I have some questions regarding the GPL/QPL versions of Qt, so here we 
> go.

Well, I'll give them a go, being something of a licensing pedant, but keep in 
mind that my advice has absolutely no real legal bearing.  :-)

> The first question: at work I am developing a library for linux, which will 
> (probably) be closed source. For testing purposes I need to write a small 
> GUI test app and I'd like to use Qt for this. Now and in the foreseeable 
> future I am the only linux-developer at work. AFAIK the GPL talks about 
> issues when redistributing software.

This is correct; if you don't redistribute the software you can link it to 
anything you want to.

> Now, I am the only person who will ever (at least in the near future) use 
> this app.  Does the GPL allow to develop an app which links to a GPL lib if 
> the resulting app isn't distributed at all ? Does the QPL allow this ?

GPL allows it.

> Second question: in the future there might be a MacOS X developer.
> I guess neither GPL nor QPL allow to give my closed source test app to him 
> (including the source), under the condition that he doesn't have the right 
> to give it away to other persons ?

There are two ways that you probably covered here.  First, since he's 
developing on a non-Linux platform, I presume that you will be giving him 
*just* source.  In this case you're fine.  (Presuming all the other copyright 
issues are in order.)

The second is in the definition of redistribution (and note that this is 
debated).  Since this is at work -- your company is one legal entity and 
presumably the copyright holder on your test application.  Your coworker is 
part of the same entity and his work is also going to copyrighted to your 
company.  As such this *probably* won't count as redistribution.

Note that I assume TT interprets the two things above this way because of a 
similar issue going the other way:  thier port of KDE to the Mac.  Because 
they are linking GPL'ed code to a proprietary lib (Qt on Mac) and presumably 
distributing binaries internally, this would only be allowed assuming the 
above two statements are true.

> Third question: it might happen that my test app becomes open source but the 
> library I'm developing stays closed source.  Would it be ok to link an open 
> source app against an open source library (Qt) AND a closed-source lib ?
> Would it be ok with GPL-Qt ? with QPL-Qt ? Which license would I have to use 
> for the app ? Would GPL be ok ?

Here you're pretty screwed.  The issue isn't with the license of your app (it 
would be pretty easy to use a GPL exception), but the OSS Qt can't be linked 
to a non-GPL / non-QPL compatible license.

Otherwise you could create an application that's just a thin wrapper around a 
proprietary "library" and link them all to a GPL'ed Qt.


- -Scott
- -- 
Audience Member: "What was the hardest part of building TeX?"
Donald Knuth: "It was all pretty easy."
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