What is Kubuntu?
Kubuntu is a free, user-friendly operating system based on the K Desktop Environment and on the award winning Ubuntu operating system. With a biannual release cycle and at least 18 months of free security updates for each release, it is the secure, stable computing environment.

Kubuntu is an official derivative of the Ubuntu operating system using the KDE graphical environment instead of GNOME. It is part of the Ubuntu project and uses the same underlying system. Kubuntu and Ubuntu can work alongside each other by installing the ubuntu-desktop and kubuntu-desktop packages.

Fedora is an RPM-based, general purpose operating system built on top of the Linux kernel, developed by the community-supported Fedora Project and sponsored by Red Hat. Fedora's mission statement is: "Fedora is about the rapid progress of Free and Open Source software.

One of Fedora's main objectives is not only to contain free and open source software, but also to be on the leading edge of such technologies. Also, developers in Fedora prefer to make upstream changes instead of applying fixes specifically for Fedora—this ensures that updates are available to all Linux distributions Linus Torvalds, creator of the Linux kernel, says he uses Fedora because it had fairly good support for PowerPC when he used that processor architecture. He became accustomed to the operating system and continues to use it.

OpenSUSE, purpose operating system developed by the OpenSUSE Project. After acquiring SUSE Linux in January 2004, Novell decided to release the SUSE Linux Professional product as a 100% open source project, involving the community in the development process. The initial release was a beta version of SUSE Linux 10.0, and as of December 2008 the current stable release is OpenSUSE 11.1.

Beyond the distribution, the OpenSUSE Project provides a web portal for community involvement. The community assists in developing OpenSUSE collaboratively with representatives from Novell by contributing code through the OpenSUSE Build Service, writing documentation, designing artwork, fostering discussion on open mailing lists and in Internet Relay Chat channels, and improving the OpenSUSE site through its wiki interface. Novell employed over 500 developers working on SUSE in 2004. Novell markets OpenSUSE as the best, easiest distribution for all users.

Like most distributions, OpenSUSE includes both a default graphical user interface (GUI) and a command line interface option. During installation, the user may choose among KDE, GNOME and Xfce GUIs. OpenSUSE supports thousands of software packages across the full range of ‎Free software / open source development.

Debian GNU/Linux is one of the most popular and influential computer operating systems composed of free and open source software. Debian is known for strict adherence to the UNIX and free software philosophies as well as using collaborative software development and testing processes. Debian can be used as a desktop as well as server operating system.

 

information acquired from website source kubuntu, fedora project, open suse, debian and wikipedia Feb 2009