KDE

KDE is an international technology team that creates free and open source software for desktop and portable computing.

Provides an innovative and mature application framework

More than 600 applications mostly under Open Source licenses and translated into dozens of languages

Plasma as a universal canvas serves as primary user interface for mobile and desktop devices on top of Qt

"For over a decade KDE and Qt have enjoyed a highly symbiotic relationship that has grown in step with our communities and technology innovations. The ability to build both with and on top of Qt has been one of its enduring strengths and one of the secrets of KDE's success."

Aaron Seigo, President of KDE e.V.

KDE 4 and Qt

KDE is a large showcase and breeding ground for Qt technologies. The Phonon framework has evolved from the KDE community and was integrated into Qt4.4. Qt Software has put a large effort in developing Phonon and returning value to KDE.

On top of Qt's QGraphicsView, Plasma can run native Plasmoids as well as Mac OS X Dashboard Widgets, Google Gadgets and others. Plasma provides unique theming, integration of web services, innovative user interface elements, and support for multiple languages such as JavaScript, Python and Ruby to developers.

The KDE platform provides higher level user interfaces and widgets, as well as APIs for more complex tasks such as hardware management, network transparency, and other common infrastructure. The KDE libraries are available under the LGPL. All of those are built on top of Qt and tailor the abilities of Qt to KDE's very needs.