<chapter id="licensing">
<title>&Qt; and Licensing questions</title>

<qandaset>

<qandaentry>
<question id="qt">
<para>What is &Qt;, by the way?</para>
</question>
<answer>
<para>&Qt; is a C++-based class library to build user interfaces. It
also includes many utility classes like string classes and classes
to handle input and output. It
provides most of the widgets you will see in a &kde; application:
menus, buttons, sliders, &etc;.  &Qt; is a cross-platform library that
allows you to write code that will compile on &UNIX; systems as well as
&Windows; and embedded devices.  You can learn more about &Qt; at <ulink
url="http://www.qtsoftware.com">http://www.qtsoftware.com</ulink>.</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>Why does &kde; use &Qt;?</para>
</question>
<answer>
<para>&Qt; is a very sophisticated toolkit that provides everything that
is needed to build a modern user interface.  &Qt; is written in C++, thus
allowing object-oriented development which ensures efficiency and
code reuse in a project the size and scope of &kde;.  In our opinion
there is no better toolkit available for &UNIX; systems and that it
would have been a grave mistake to try to build &kde; on anything but
the best.</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>Why does &kde; not use GTK, XForms, Xlib, whatever?</para>
</question>
<answer>
<para>There are a number of toolkits available.  To provide a
consistent user interface and to keep used resources such as memory to
a minimum, &kde; can use only one of them.  &Qt; was selected for the
reasons mentioned above.</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>But &Qt; isn't free, is it?</para>
</question>
<answer>
<para>It is!  As of September 4, 2000, version 2.2 of the &Qt;
libraries were licensed under the <acronym>GPL</acronym>, thereby
fulfiling all aspects of <quote>free software</quote>. Since version 4.5.0
Qt is also available under the <acronym>LGPL</acronym>.</para>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>Can I write commercial software for &kde;?</para>
</question>
<answer>
<para>You can use the &kde; libraries to write <quote>commercial and
closed source</quote> as well as <quote>commercial and open
source</quote> software. If you want to write open source software you can
use the &Qt; free edition.  But if you intend to write closed source software
you may not use the &Qt; free edition; you need to obtain the &Qt;
professional edition from Qt Software.</para> <para>If you want more
information, please contact <ulink
url="http://www.qtsoftware.com">Qt Software</ulink> directly.</para>
</answer>
</qandaentry>
</qandaset>
</chapter>
