Who is Richard Stallman? What is GNU?
Richard Stallman (a.k.a. RMS) is considered to be the founding father of free software. He began thinking about the issue while he was working in the Artificial Intelligence Laboratory at MIT. The lab used a printer that often broke down, but because the lab workers had the source code of the printer's driver (1) at their disposal, they were able to modify the program so that the printer would send an error message to everyone's workstation every time it broke down and whoever was available would go the the printer room and fix the problem.
One day the lab bought a new, more reliable printer from Xerox. Unfortunately, the source code of the printer driver was not included in the package, and they were unable to put in place the same kind of maintenance set-up they had used before. Richard Stallman later heard that another scientific laboratory had a copy of the source code of the Xerox driver. When he tried to obtain it, he was told that the lab had agreed to keep the source code to themseves and not to make it available to anyone else. Stallman was quite offended by this selfish attitude, and it was then that he became aware of the dangers of a proprietary system.
Richard Stallman then decided to create the Free Software Foundation. Knowing full well that it is impossible to use a computer without an operating system, it became clear that the first project of the foundation should be to put together a complete and free operating system... the GNU project (2). The operating system would be compatible with Unix, yet different. Such an operating system now exists... it is called GNU/Linux.
To authenticate this new system a new legal basis had to be created; and so was born the GNU GPL (GNU General Public License). The GNU GPL is the free software license par excellence. It sets forth distribution conditions that guarantee freedom for its users. A program protected by the GPL is free, but the GPL also stipulates that all programs derived from such a program conserve the same freedom.
Richard Stallman is also a highly talented programmer, the author of many free software applications such as GNU Emacs, GCC, GDB, and is very active in the development of new free software applications.
 .A driver is the software piece that is used to access to and use the printer.
 GNU is a funny recursive acronym meaning GNU's Not Unix.
English translation by Katixa Rybalka.