"KDE is one of the two most frequently used Linux desktop
environments, and it includes desktop widgets, an instant messenger
client, multipaned file and web browsing, the Amarok music player
and the Digikam photo manager -- some of the best that open source
has to offer. KDE has accumulated a huge userbase, and the last 18
months have seen it move from version 3.5 to version 4.2. The
toolkit that has always provided most of the functionality behind
KDE is called Qt, a commercial suite of libraries and APIs released
using both open-source and proprietary licences. Fourth-generation
KDE applications use fourth-generation Qt, and part of that upgrade
involves a commitment to cross-platform compatibility. Despite the
fact that Qt has been mostly cross-platform for some time, it still
takes a considerable amount of effort to create portable KDE
applications out of the older code base. That's why the move to
true portability has taken so long, and why the February release of
KDE is so significant."