GNU is an extensive collection of free software, which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operating systems popularly known as Linux. Most of GNU is licensed under the GNU Project's own General Public License (GPL).
Richard Stallman, founder of the GNU project
Free software, libre software, or libreware is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, not price; all users are legally free to do what they want with their copies of a free software regardless of how much is paid to obtain the program. Computer programs are deemed "free" if they give end-users ultimate control over the software and, subsequently, over their devices.
Creating a 3D car racing game using the Blender Game Engine.
Although nearly all computer viruses only affect Microsoft Windows, antivirus software such as ClamTk (shown here) is still provided for Linux and other Unix-based systems, so that users can detect malware that might infect Windows hosts.