Different users can work on the same machine at de same time.
An advanced architecture of security keeps different processes in different spaces, where they cannot influence each other. The GNU Project was launched in 1983 by Richard Stallman, and aims to construct a free unix-like operating system. Commercial unixes were becoming gradually less popular, not because of technical shortcomings, but because of too high license fees, closed source and not too good interoperability of different species. A Brief History of Hackerdom , by Eric S. Raymond, the man behind the Open Source Movement. Richard Stallman founded the Free Software Foundation , to raise funds for supporting open-source development.