KDE has changed over the past 13 years. The application framework has grown, matured and gone cross-platform, as have the applications. Strong growth in our community has created an increasingly diverse and large set of high-quality applications.
In the process, KDE's identity has shifted from being simply a desktop environment to representing a global community that creates a remarkably rich body of free software targeted for use by people everywhere.

KDE is no longer software created by people, but people who create software.

To be able to communicate this clearly in our messaging, it is necessary to reposition the KDE brand so that it reflects the reality. We therefore also need distinct brands for the products we produce.

Summary

* We will use simply "KDE" and retire the expansion "K Desktop Environment"
* We will use "KDE" exclusively in two meanings:

Full Story here

Also: Why the rebranding?