Re: GPL only

faq
flatforty
contribute
subscribe
configure
search
rdf

main
parent
thread

Re: GPL only
by David Johnson on Tuesday 17/Jun/2003, @16:24

That's like saying you can vote for whichever candidate you want, so long as you vote for the one Trolltech wants you to vote for. It's not a BSD licensed app if it must be licensed under the GPL.

Related Links

·   Articles on Qt
·   Also by David Johnson
·   Contact author

The Fine Print: The following comments are owned by whomever posted them.
( Reply )

Re: GPL only
by Simon Farnsworth on Tuesday 17/Jun/2003, @16:33

If I'm interpreting correctly, the app+Qt combination is GPL licenced on the Mac; if you ship a binary dependant on Qt/Mac, that binary as a whole is under the GPL. If your app is also available under another GPL-compatible licence, the end user can obtain that application under *that* licence, and is only then forced back to GPL if they distribute a Qt/Mac binary based on the free edition of Qt. If they use the commercial edition of Qt, they are not forced to GPL the combination.

[ Reply To This | View ]

Re: GPL only
by Jim Dabell on Tuesday 17/Jun/2003, @16:42

No.

You write code. The copyright on this particular code belongs to you. This work can be licensed however you want. Let's say you pick a BSD-style license.

When linking it to the QT toolkit, you are creating a derivative work (the binary) based upon both your work and Trolltech's work. Now, you need a license from Trolltech to distribute this.

Trolltech offer a number of licenses. If you are linking against the Mac edition, you have the opportunity of paying them for a license (the "commercial" license option), you can choose the evaluation license (which expires after 30 days), or you can choose the GPL license.

The first two options let you distribute the derivative work however you see fit. The GPL has a clause that requires any derivative works to fall under the GPL license.

Now, somebody else comes along. They may want to distribute the derivative work under the GPL. That's okay - since you offered your copyrighted work to the public via the BSD license - which allows incorporation into any and all derivative works without any other requirements. They can therefore distribute the derivative work under the GPL. This is what is meant when people talk about "GPL-compatible licenses".

Now, another person comes along. They have a commercial license for QT, and wish to distribute the derivative work in binary-only form. This is also okay - your work is under the BSD license, which allows incorporation into any derivative works, and they already have a license saying that it's okay for them to do the same with Trolltech's work.

At no point has your original work not been available under the BSD license. If people have a commercial license for QT, they can give away binary-only forms of your work. If they port it to a platform where QT is available under the QPL, they can link it with that and give away binary-only forms of your work. If they partially rewrite it so that it uses a different toolkit, they are subject to that toolkit's licensing constraints.

It is only the Trolltech original work's license that is restrictive - you are free to license your work any way you see fit, and you can pick the BSD license if you so desire. But you can't relicense Trolltech's works for other people, you can only ask them (politely) to offer licenses that you want them to.

[ Reply To This | View ]

Re: GPL only
by David Johnson on Tuesday 17/Jun/2003, @19:07

<snip>When linking it to the QT toolkit, you are creating a derivative work (the binary) based upon both your work and Trolltech's work. Now, you need a license from Trolltech to distribute this.</snip>

Linking does not create a derivative work. In the case of static linkage, the GPL applies because you are actually distributing the library along with the binary. But in the case of dynamic or runtime linkage, you are not copying, modifying or distributing the GPLd work, so the GPL should not apply. Trolltech and the FSF disagree, put here's a link to an informed and educated counter-opinion by the general counsel of the Open Source Initiative: http://rosenlaw.com/html/GL18.pdf.

I don't have my own team of lawyers, so I find it easier to simply ask Trolltech to offer Qt/Mac under the same terms as Qt/X11, rather than challenge them on the matter in court.

[ Reply To This | View ]

Re: GPL only
by anon on Tuesday 17/Jun/2003, @19:29

It's simple: Even dynamic linking creates a derivative work.

The reasoning is not legal, it's technical. Dynamically linked binaries contain information from the libraries against which they were linked against. In the case of linking your application against Qt, you are incorporating code compiled by from the Qt headers (which is under the GPL) in your binary.

[ Reply To This | View ]

Re: GPL only
by Jim Dabell on Wednesday 18/Jun/2003, @04:50

Linking as "creating a derivative work" is so widely accepted in the community that I would certainly not want to go against it. That's a good link David, I was aware of the position, but unaware of the document to go with it. Thanks.

I personally disagree with the technical reason you cite, anon. Otherwise, merely cloning the interface would be enough to infringe on the copyright (remember Harmony?). There are fringe cases such as macros though.

[ Reply To This | View ]

Re: GPL only
by anon on Wednesday 18/Jun/2003, @08:58

Well it does mean that, and as far as I know it is true.

If you clone the interface/macros etc in a clean room manner, then you've hit the jackpot. Of course you have to link against your clone and make sure it actually works with the real Qt.

Logical conclusion...

[ Reply To This | View ]

Re: GPL only
by David Johnson on Wednesday 18/Jun/2003, @11:17

<snip>Dynamically linked binaries contain information from the libraries against which they were linked against</snip>

The information they contain is limited to a reference to an interface. You are using the library in its intended manner through a published API. Absolutely no code from the library is incorporated into the application. A good analogy is a hyperlink on a webpage. Does that hyperlink indicate derivation from the linked page?

p.s. Macros and inlines may be an exception. If there are few of these then Fair Use may allow their fair use [sic]. If there are a lot of them, the argument might still be made that implementation has been placed into the API allowing it to be used by the intended and customary mechanism.

[ Reply To This | View ]

The Fine Print: The previous comments are owned by whomever posted them.
( Reply )


		"We could write better than CORBA. Hic. In a day!" -- Preston Brown, Matthias Ettrich
KDE®, "K Desktop Environment", "KDE Dot News", "got the dot?" and the KDE Logo® are trademarks or registered trademarks of KDE e.V. in the European Union, the United States and other countries. All other trademarks and copyrights on this page are owned by their respective owners. Comments are owned by the poster. The rest: Copyright © 2000-2008 KDE e.V. for The KDE Project. For further information or comments on this site, please contact the Webmaster.