Linux is an entirely open source project. That means that anyone, even you, can download and change the source code as you please. Because of the free and open nature of Linux, different distros, such as Ubuntu, Fedora, and OpenSUSE, have evolved. This evolution has also branched into the main types of desktop managers regularly used by Linux users: KDE, Xfce, and Gnome. And all of them are free without charge, with some distributions even giving away free CDs (Ubuntu) and ISO downloads from their websites.