Qt License & Qt vs Java

Qt License & Qt vs Java

Post by Alec » Fri, 08 Mar 2002 09:51:05



Hi

Is Qt really open-source, if  so, why are they (trolltech) selling it? I
mean, how  do they motivate users to pay for what's free?  Also, does Qt
library really make a viable tool for multi-platform programming? How does
it compare to Java?

Thanks
Alec

 
 
 

Qt License & Qt vs Java

Post by Terran Melconi » Fri, 08 Mar 2002 10:12:36




>Is Qt really open-source, if  so, why are they (trolltech) selling it? I

QT is available under the Gnu GPL, which requires users to make source
available.  If you pay for it, you can use it in commercial
applications which you distribute without source.  I'm sure there's a
FAQ on this somewhere...

Here you go:

    http://www.trolltech.com/developer/faqs/simple.html

 
 
 

Qt License & Qt vs Java

Post by Stuart Lamb » Fri, 08 Mar 2002 10:53:24



>Hi

>Is Qt really open-source, if  so, why are they (trolltech) selling it?

Yes -- and no.

The X11 version of Qt is available under the GPL. ie: you use Qt without
paying for it, your app must be GPLd. Trolltech owns the copyright to Qt,
so they are able to relicense it in any fashion they see fit. This means
that they can (and do) sell a commercial license for Qt to anybody who
wishes to use it.

Note that the Windows and Mac OS X versions of Qt are *not* GPL.

Quote:>I mean, how  do they motivate users to pay for what's free?

By letting those who pay for it use it in a fashion that is not
compatible with the GPL. It's basically saying, "We will give you
access to Qt at no cost, as long as you give access to your program's
code to the world at large. If you don't like that, we will give you
access to Qt for $BIGNUM, and let you use it without having to disclose
your source."

Trolltech can do this because, and *only* because, they hold the
copyrights to Qt. The GPL version is out there, and cannot be recalled,
but they are within their rights to relicense for those that persuade
them to do so (in this case, by paying out a sum of money.)

Quote:>Also, does Qt
>library really make a viable tool for multi-platform programming?

As long as you are prepared to pay for the Windows/Mac versions of
Qt, yes. If you aren't prepared to pay in this fashion, you can only
port your application to X11 systems (Linux, Solaris, HP-UX, AIX,
Irix, Darwin, etc.) unless you bother to port Qt to some other
platform.

Personally, I'd be happier if Trolltech released the Win/Mac versions
in the same way they have released the X11 version. However, as the
copyright owners, they are well and truly within their rights; and we
should be grateful for at least the X11 version. It's a very well
documented library; I'd argue that the documentation is more accessible
than gtk's. Pity about the choice of language, though (C++ is not my
language of choice - personal preference.)

--
"You didn't slay the dragon?!"
"It's on my to-do list, now come on!"
  -- Shrek.

 
 
 

Qt License & Qt vs Java

Post by Kevin Kramme » Fri, 08 Mar 2002 20:01:33



> Personally, I'd be happier if Trolltech released the Win/Mac versions
> in the same way they have released the X11 version. However, as the
> copyright owners, they are well and truly within their rights; and we
> should be grateful for at least the X11 version. It's a very well
> documented library; I'd argue that the documentation is more
> accessible than gtk's. Pity about the choice of language, though (C++
> is not my language of choice - personal preference.)

I think there is some kind of non-commercial licence for the Windows
version available.

This is a link, seems to be Qt2.3 only
http://www.trolltech.com/developer/download/qt-win-noncomm.html

Cheers,
Kevin

--

Student at Graz University of Technology
http://www.sbox.tu-graz.ac.at/home/v/voyager

 
 
 

Qt License & Qt vs Java

Post by Paul F. Ku » Sat, 09 Mar 2002 02:23:57



> Hi

> mean, how  do they motivate users to pay for what's free?  Also, does Qt
> library really make a viable tool for multi-platform programming? How does
> it compare to Java?

   I have an application that has a core written in C++ and only the
GUI and the graphics drawing in Java.  I've partially re-written the
GUI and graphics with Qt so I can compare the two.

   Altho the GUI is simple, Java is significantly slower at
application startup.  Even on second startup where the JVM is
presumably already in virtual memory.  Qt is much quicker to start up,
especially on second startup where it is lightingly fast (never seen an
application startup so quickly).

   For the simple graphic drawing (all straight lines), Qt is
noticeably faster.  However, the origin of my drawing algrorithms is
in the C++ code and must go thru the JNI to get on the sceeen.

   A significant difference is that the Java GUI and graphic drawing
is very slow over the network, even betwen two machines on the same
subnet, no less over the Internet.  With Java coming from a company
whose motto is "the network is the computer" this is sad.

   There a bugs in Java that get introduced with newer releases.  For
example, starting with Java SDK 1.3, the Java PrintJob class only
shows a small postage stamp sized window under KDE, while it works
fine with GNOME and earlier versions of Java.  This is not fixed with
Java 1.4.  However, with Java 1.4, another printing bug was
introduced.  Namely, you can not print to a PostScript file if you
machine doesn't have a printer defined.   Serious problem for laptops.

   There are yet more problems with a mixed C++/Java application like
you have to use a C++ compiler that is binary compatible with the one
the JVM was compiled with.  So forget about using gcc 3.x or even Red
Hat's gcc 2.96.  You could try compiling Java from source with gcc
3.x, but it doesn't compile.  However, with Qt you get source, even
when you license the Windows version, so you have control over which
compiler you want to use.

   I could go on, but the bottom line is that I think I'll be much
happier with my cross platform application after I've completely
converted over to Qt.

 
 
 

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