This program is free software; this means that everyone is free to use it and free to redistribute it under certain conditions. This program is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of this program that they might get from you. The precise conditions are found in the GNU GPL (General Public Licence). The program manual is covered by the GFDL (GNU Free Documentation License). This license is similar in spirit to the GNU General Public License, but is more suitable for documentation.