[OT] GP, Qt (was Re: ready to use python, need help with GUI decision

Ville Vainio ville at spammers.com
Tue Mar 9 19:20:16 CET 2004

>>>>> "David" == David MacQuigg <dmq at gain.com> writes:

    David> What I'm saying is that if you are in this rare situation,
    David> can't afford the licesne, and not sure your product will
    David> ever be sold, you just have to be careful not to release
    David> the product before paying your dues.  The only "danger" I

It's not only about creating a product that might or might not be sold
- it's about creating a product than can run on win32. Also, I'm not
absolutely certain that the Qt commercial license allows this - what's
there to stop a big company developing all the software with GPL
version of Qt, and finally release the version that is "mastered" by a
commercially licensed Qt?

    David> claim it as GPL and avoid paying your license.  Maybe I'm
    David> misunderstanding the problems and dangers you forsee.
    David> Could you be more specific?

A part of it is the fact that quite often there is a lot of
"convincing" to do to be able to choose a specific platform for
developing a product. If you were trying to push Linux/Python/Qt
combo, you would have to convince people to shell out
$1550/developer/YEAR. That's (much?) more expensive than Windows
development tools, and is not going to work well as an argument. You
minimize the risk of being shot down by suggesting something like
wxPython instead.

Also, if you choose to develop a considerable piece of commercial code
in Qt, you develop a large codebase that is dependent on the library
(and can't be trivially rewritten to use another toolkit). This might
mean you need to keep paying Trolltech until the end of the world. It
might be an expensive mistake, esp. if you had the option to choose a
free toolkit.

    >> I would suggest instead that all the "valuable", back end parts
    >> of a program be coded UI-independently (good idea in any case),

    David> license at all.  I also question the legality.  It gets
    David> down to a question of whether "connecting via CORBA" is
    David> equivalent to "linking".  There is certainly more danger in

Of course it isn't. It is anologous to accessing a Samba share - it
would be ridiculous to connect the license of network server with the
license of clients that access it. Well, I guess that might be a
standard practice in some (very) proprietary environments, but I would
steer clear of such systems...

    David> on the GPL end.  It seems like what you are suggesting is
    David> no different than releasing a program under GPL, but
    David> with-holding a key piece for which you charge a license.

This is entirely doable. It might also be the only option if your
company opposes GPLing their code at any cost, and you feel you would
benefit from using a GPLd subsystem. GPL doesn't forbid this: if the
key piece is trivial to implement, people will implement it and use a
completely GPL'd version.

    David> deal at that point.  I have never understood the intensity
    David> of this debate over the Qt licenses.  I guess I never will.

See http://www.tbray.org/ongoing/When/200x/2003/07/12/WebsThePlace
("Are You a Sharecropper?").

I appreciate the power of the Qt toolkit, and the wonderful DE they
have built on it and which I use exclusively ATM (KDE; 3.2
rocks). It's just that I wouldn't use it for my own code, and wouldn't
recommend anyone who doesn't understand the implications to do so -
esp. a newbie that's looking for a nice toolkit to use for a small
project at work. Such decision has to be made when you are completely
aware of all the gotchas.

LGPL are BSD libraries are worry free, and can be safely used at all
times. If you are using a GPL'd or a proprietary library you are
playing with fire, and you should be aware of the consequences.

Ville Vainio   http://tinyurl.com/2prnb

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