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 software distributed under a free and open source license, but also to be on the leading edge of such technologies. Fedora developers prefer to make upstream changes instead of applying fixes specifically for Fedora—this ensures that their updates are available to all Linux distributions.
Fedora has a comparatively short life cycle: version X is maintained until one month after version X+2 is released. With 6 months between releases, the maintenance period is about 13 months for each version.
Linus Torvalds, author 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.
According to Distrowatch, Fedora is the second most popular Linux-based operating system as of mid 2009, behind Ubuntu.
Debian is a computer operating system composed of software packages released as free and open source software especially under the GNU General Public License and other open source licenses. The primary form, Debian GNU/Linux, which uses the Linux kernel and GNU OS tools, is a popular and influential Linux distribution.
It is distributed with access to repositories containing thousands of software packages ready for installation and use. Debian is known for strict adherence to the Unix and free software philosophies as well as using collaborative software development and testing processes.
The Debian Project is governed by the Debian Constitution and the Social Contract which set out the governance structure of the project as well as explicitly stating that the goal of the project is the development of a free operating system.
Thus, the Debian Project is an independent decentralized organization; it is not backed by a company like other Linux distributions such as Ubuntu, openSUSE, Fedora, and Mandriva. The cost of developing all the packages included in Debian 4.0 etch (283 million lines of code), using the COCOMO model, has been estimated to be close to US$13 billion.
Ubuntu is a computer operating system based on the Debian GNU/Linux distribution. It is named after the South African ethical ideology Ubuntu ("humanity towards others") and is distributed as free and open source software. Ubuntu provides an up-to-date, stable operating system for the average user, with a strong focus on usability and ease of installation. Ubuntu has been selected by readers of desktoplinux.com as the most popular Linux distribution for the desktop, claiming approximately 30% of Linux desktop installations in both 2006 and 2007.
Ubuntu is composed of multiple software packages of which the vast majority is distributed under a free software license (also known as open source). The main license used is the GNU General Public License (GNU GPL) which, along with the GNU Lesser General Public License (GNU LGPL), explicitly declare that users are free to run, copy, distribute, study, change, develop and improve the software. Ubuntu is sponsored by the UK based company Canonical Ltd., owned by South African entrepreneur Mark Shuttleworth. By keeping Ubuntu free and open source, Canonical is able to utilize the talents of community developers in Ubuntu's constituent components. Instead of selling Ubuntu for profit, Canonical creates revenue by selling technical support and from creating several services tied to Ubuntu.
Canonical endorses and provides support for three additional Ubuntu-derived operating systems: Kubuntu, Edubuntu and Ubuntu Server Edition. There are several other derivative operating systems including local language and hardware-specific versions.
The Linux kernel is a Unix-like operating system kernel. It is the namesake of the Linux family of operating systems. Released under the GNU General Public License version 2 (GPLv2) and developed by contributors worldwide, Linux is one of the most prominent examples of free software.
The Linux kernel was initially conceived and assembled by Linus Torvalds in 1991. Early on, the MINIX community contributed code and ideas to the Linux kernel. At the time, the GNU Project had created many of the components required for a free software operating system, but its own kernel, GNU Hurd, was incomplete and unavailable. The BSD operating system had not yet freed itself from legal encumbrances. This meant that despite the limited functionality of the early versions, Linux rapidly accumulated developers and users who adopted code from those projects for use with the new operating system.