[PyKDE] qt, pyqt license

[Jonathan Gardner]

On Tuesday 18 February 2003 05:21, david wrote:
> Dear all,
>
> I don't understand the licence for qt and pyqt. On X11, it's GPL and on
> Microsoft Windows, it's what ? Commercial licenses and a
> free-as-in-free-beer for older version. That's very disorder !
> I have not a good idea for the future...
> which choice pyqt or pygtk ?
>

My understanding is that Qt is free on X11 as long as you are writing free 
software. Qt is not free if you want to write non-free software on X11. If 
you want to use Qt for windows, you need to pay no matter what.

The confusion about the Windows version is because they recently changed their 
licensing with Windows when they released Qt 3.0.

Here's a page that spells that out in more detail:
http://www.trolltech.com/products/licensing.html

As far as PyQt is concerned, Phil has a similar licensing scheme. You can read 
about it on this page.
http://riverbankcomputing.co.uk/pyqt/index.php

The reason why there is a license duality is because of the GPL. The free 
software version of Qt is licensed under the GPL, so if you want to use it, 
you have to agree to writing free software. This makes all the people who use 
Linux, and all the companies who put together distributions of linux happy.

But this is bad because you cannot then sell software using the Microsoft 
model. The GPL intentionally prevents this. So Trolltech and Phil say "If you 
pay me, I will license my software under a different license for you". This 
makes everyone else who doesn't want to work the Linux way happy.

So now you have a choice if you want to write Qt software on X11. You can 
either write Free Software, or you can try to make a money and write not-free 
software.

Qt's opinion on Windows is that as soon as they make the windows source code 
licensed under the GPL or BSD or something like that, they will not produce 
any more software for it for free. I think it is because it is so hard to 
maintain code for Windows systems, but that is my opinion.

-- 
Jonathan Gardner
jgardn at alumni.washington.edu
Python Qt perl apache and linux