Petition for TrollTech to GPL Qt

TrollTech [ ], a small Norwegian company, have an excellent C++ GUI toolkit called Qt. If C++ is your language of choice, you'll like Qt. They recently proposed a licence change [ ] to an Open Source licence they dubbed QPL [ ].

I'd like them to release Qt under the GPL (GNU's General Public Licence), possibly with additional permission to dynamically link with software produced under the Qt Professional Edition licences, Artistic Licence or whatever.

Here is the petition [ ], which has been delayed due to a flurry of new entries in the last couple of days. Current target is between Christmas and New Year.

Why GPL?

TrollTech make money by charging for the right to use Qt in proprietary products, and for support. So the GPL, which disallows such use, supports this model: it is a feasible option (see FAQ).

The GPL is not compatible with the QPL (see FAQ). This means that the KDE project [ ] still have to get additional permission from all their authors to link with the Qt library. It also means that they can't KDE-ize entire apps without doing the same thing, or reuse existing code (eg. GNU Ghostscript, GNU Plot, Electric Eyes, etc.). Debian and RedHat are becoming increasingly strict about licences, and they wouldn't distribute such problematic binaries.

The greatest benefit of releasing Qt under the GPL is that it reduces the barriers for code sharing between KDE and Gnome [ ] apps (see FAQ). Having two or more open-source desktops compete on merit is a Good Thing, but stealing each others code in large or small lubricates the evolution of both.

The GPL is also my personal preferred licence, and I don't want to create problems for someone wanting to create a Qt GUI for something I write.

Are You People Never Happy?

There's a reason that TrollTech put their licence out there for comment. They want feedback, and this is mine; you're doing them no service by waiting until afterwards to complain.

I've found the Trolls to be enlightened people; it's the details which bit them in the past. I wouldn't want that to happen again if I can help.

Do Petitions Work?

I honestly don't know, but silence is unlikely to work. When the signatures start dribbling off, I'll send it off to TrollTech and post it on the web page.

How Do I Sign?

Simply send EMail to `', in the following form:
Name (1 line, eg.  Paul `Rusty' Russell)
EMail (1 line,eg.,
Bio (1 line, eg.  Linux Kernel IP Firewall Maintainer)
Comment (multi line; I may include some, none or all in the final petition)

I Think You're An Idiot.

That's fine, but telling me is going to waste twice as much time as mumbling about it to yourself. Maybe I'll fail miserably and then you can laugh at me. Whatever.

Why You?

I think everybody tried to get TrollTech to change their licence at some stage; me among them. I really got along well with the Trolls I've met, and I always felt that they have come so close that it'd be a pity if an Achilles Heel were to stop their march to world domination.

Plus, noone else was doing it.


A number of important questions have been raised, and a number of points hammered home to me since this petition was put up.

Code Sharing Between Gnome and KDE

David Kastrup clarified the following: the core Gnome libraries are all LGPL, meaning that KDE (and anyone else) are allowed to use their libraries anyway.

KDE apps cannot reuse Gnome code in other ways, nor can an existing Gnome app be KDE-ized, since these apps are generally GPL (not LGPL).

Thanks to David for this clarification, and I apologize if people found my previous misleading statement, er.... misleading.

Why is Qt incompatible with the GPL when the X11 licence isn't?

A number of people asked this, so I passed the buck to the author of the GPL, Richard Stallman: A number of people have asked me why the QPL licence is incompatible with the GPL, when the X11 and zlib licences apparently are compatible (as far as linking with these libraries goes). The X11 distribution terms are so permissive that they let you add just about any license you prefer, when you make a derivative or combined work. In particular, you could add the GPL. Thus, when you combine Xlib and some GPL-covered program, the combination can be distributed as a whole under the GPL. The QPL doesn't allow this; you cannot include Qt in a combination which is covered by the GPL. Thanks RMS.

Why not LGPL?

Paul Iadonisi and David Schweikert thought I should change my petition to LGPL. Rick Macdonald asked for clarification `How can the GPL both disallow and support "this model"?'

Rick Macdonald suggested I clarify as follows: TrollTech makes money by charging for the right to use the Qt Professional Edition in proprietary products, and for support. The QPL is designed to protect their sales of the Professional Edition. The GPL also disallows such use, and therefore offers the same protection. It is a feasible option for TrollTech to use the GPL.

My proposal is "GPL, possibly with additional permission to dynamically link with software produced under the Qt Professional Edition licences". The second part is important for Troll.