They are bundled as the default environment with a number of free software operating systems, such as Chakra,[6] Kubuntu,[7] Mageia (DVD version),[8] openSUSE,[9] or TrueOS.

The Kross scripting framework allows developers to write widgets in a variety of programming languages in addition to C++.

[14] It replaces the dialog box "Run Command" from K Desktop Environment 3, and also inherits from the application launcher feature, expanding the possibilities through a modular plug.

In KDE 4.3, replaced by the new Air theme, which predominates in transparency and white as base color.

[27] Replacing an earlier tablet prototype,[34] Contour has then become the main workspace UI of Plasma Active and was shipped as 1.0 in October 2011.

[30] Plasma Mobile was targeted at smartphones and small tablet devices that are mainly used via touch input.

It was originally expected to be released in 2011 along with Plasma Active 1.0 but development focus shifted towards Contour.

Linux.com described the reaction from users as a "revolt", writing that the backlash KDE 4.0 received was on a scale that was unprecedented for a FOSS project.

Although it was a developer's release, several distributions made the KDE 4.0 desktop environment available to their users without specifying that it was an experimental option.

A number of KDE developers, including project leader Aaron Seigo, were targeted for abuse by outlets like Linux Hater's Blog.