QT can refer to several things. There's the QT widget set made by Troll Tech and used in KDE. That used to be evil and not free so to GNU purists it was the devil. Since then the X11 libraries for it went GPL in version 2.2. I'm still critical of it, though, because it still sucks, still uses heavily preprocessed C++, and still isn't free for non-X11 platforms like Win32 or framebuffer. QT is also a common abbreviation for QuickTime among Mac buffs.

This is also used by idiot AOL-using teenage girls to mean "cutie".
Qt/Unix 2.2 is dual-licensed under the GPL and QPL. This means you can choose either license.

Unfortunately, only Qt for the X11 platform is thus licenced. However, given time I think we will have GPL'ed versions for every platform, because now anyone may legally port Qt to whatever platform they want, be it Windows, Mac or Palm.

Any such effort will probably force Trolltech into GPL'ing Qt on the platform in question, since they don't want to loose their control over Qt. Widely used, unofficial ports, would not be a good thing for Trolltech. By releasing Qt under the GPL also on this platform, they regain control of their brainchild, and probably stop the forked port in its tracks. Who wants an unofficial Qt port when they can get an up-to-date, offical version with identical licencing terms as the port?

One of the most important consequences of this change in license, is that KDE is now without licencing conflicts. Before, the more restrictive QPL license triggered a clause in the GPL, making distributing any binary file where GPL'ed code is linked with Qt illegal. This is now not a problem, since Qt has the same licence as KDE; the GPL.

Some intresting quotes:

Richard Stallman:

  • "I am very pleased to see that Qt is now available under the GPL. This is a big win for free software and a great gift from Trolltech to the community."

  • (on KDE): "Also, where code was copied from other GPL-covered programs, their copyright holders need to be asked for forgiveness. To lead the way, the FSF hereby grants this forgiveness for all code that is copyright FSF. More precisely, those who as of September 4, 2000 have used some FSF code in violation of the GPL solely by linking it with Qt, and thus have forfeited the right to use that code under the GPL, will once again have full GPL permissions to use that code upon switching to a GPL-covered version of Qt. I appeal to all the other copyright holders of affected code to grant similar forgiveness and thus help resolve the situation quickly."

Eirik Eng, president of Trolltech:

  • "The release of Qt 2.2 under the GPL license will reinforce our commitment to the open source and free software movement. The GPL and QPL are similar, both having the intent of encouraging development of free software. We have many users who enjoy using Qt under the QPL license because they can choose the open source licensing they use, such as the BSD and Artistic licenses, but there has also been a demand for a GPL license. We have now provided our users a choice."

Wichert Akkerman:

  • "Debian is excited to see Trolltech take this step. This will encourage the acceptance of Qt as a building block for free software."

Matthias Ettrich:

  • "While Qt was without a doubt the best technical choice, some members of the free software community didn't agree with Qt's licensing. Thanks to Trolltech's new licensing scheme, the upcoming KDE-2.0 will receive full acceptance throughout the community."


I've been looking at & learning the QT Library, and ... wow, it's nice. :)

At first, one feature bothered me a bit. QT generates "MOC" files. MOC stand for meta-object compiler. If you write any classes that use QT's signal/slot calling system, you have to run your header through the MOC, compile the output, and link it with the rest of your object files.

However, after spending a few hours writing a kickass Makefile, all of that is done automatically.

QT 2.2 now (maybe before, and I just didn't notice?) has a QSocket class which abstracts TCP/IP sockets. I whipped out a nice (though, simple) plaintext chat application in a single day.

Now that I'm lovin' QT in Linux, I wanted to see what's involved in using it for Windows. Well, crap, it's more than $1000 (US) per developer license. That's what they do. They write a great GUI toolkit, hook the poor, innocent Linux developers, then charge them if they want to actually make their programs available to the masses. I mean... really. I've seen MFC. I've seen the beautiful code that results from using QT. After seeing how it's done RIGHT, I don't know if I'll ever bother to learn MFC.

There's a somewhat less famous QT as well -- QT is the common name for QuikTrip, a chain of convenience stores found in larger cities in the midwest United States. (Officially, the list includes St. Louis, Atlanta, Tulsa, Des Moines, Cedar Rapids, and a few others, including the inevitable outlier, Phoenix.)

As such things go, QT is actually a rather good convenience store. The prices are entirely too high (as is normally the case -- you have to pay for your convenience somehow) on most merchandise, but they always have competitive prices on gasoline. They even guarantee that if their brand of gas somehow damages your engine, they'll reimburse your repair expenses.

Having done more than my share of driving, and having visited more than my share of hole-in-the-wall shops, QT stores are actually a welcome sight. They're uniformly well-lit, clean, safe stores where you're not likely to be gang-raped in the men's room or suffer any other similarly unpleasant fate.

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