What's GNU? GNU is Not Unix! The GNU operating system was started in 1983 by Richard Stallman. The most common use of the GNU OS today is with the Linux kernel. To help clarify the inclusion of Linux with GNU, we refer to the system as a whole as GNU/Linux, although this is often known as simply 'Linux'.
GNU users who have never heard of GNU is a useful article to read if you are unfamiliar with GNU.
For many people, Linux is the one thing they have heard of when discussing free software and the GNU/Linux system, and for good reason. The Linux kernel is a wonderful example of free software and open source development. When combined with the GNU OS, millions of people all over the world can experience a free software operating system, which can replace or accompany their existing Windows or Mac OS X system.
There are many variations of GNU/Linux out there, including Ubuntu, Debian, Fedora, SuSE, Mandriva, Red Hat and Slackware - all of these systems have several common components, aside from GNU/Linux and so we call these variations, distributions, and they are distributing GNU/Linux with much extra software, including OpenOffice, Firefox and Inkscape in order to make it useful for you to use.
When we speak of Free Software, we refer to software with freedom, not price. In the case of software, Richard Stallman realised that most software, including that from Microsoft, Apple and Adobe did not respect the users, and instead forced them to agree to never share their software with their friends, never to attempt to change their software, and even to put restrictions on how and where they could use the software. In order to ensure this didn't happen with the GNU OS, he came up with a list of four essential freedoms that all software in the GNU OS should have, in order to respect your rights.
- The freedom to run the software, for any purpose
- The freedom to study and modify the software.
- The freedom to distribute copies of the software, to help your friends.
- The freedom to distribute your own modified versions of the software, to improve and enhance it.
Most of the software in your typical GNU/Linux distribution will have these four freedoms, and some distributions, such as gNewSense only distribute software that has these rights.
Open Source is a way of writing better free software. Software that is Open Source is also Free Software, but is generally targetted more at programmers than at the general public. For example, you might hear someone refer to PHP as an Open Source Programming Language - that is true, however PHP is also Free Software.