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Chapter 8
Appendix
GNU General
Public License
Version 2, June 1991
Copyright © 1989, 1991 Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-
1301 USA
Everyone is permitted to copy and distribute verbatim
copies of this license document, but changing it is not
allowed.
Preamble
The licenses for most software are designed to
take away your freedom to share and change it. By
contrast, the GNU General Public License is intended
to guarantee your freedom to share and change free
software - to make sure the software is free for all its
users. This General Public License applies to most
of the Free Software Foundation’s software and to
any other program whose authors commit to using it.
(Some other Free Software Foundation software is
covered by the GNU Lesser General Public License
instead.) You can apply it to your programs, too.
When we speak of free software, we are referring to
freedom, not price. Our General Public Licenses are
designed to make sure that you have the freedom to
distribute copies of free software (and charge for this
service if you wish), that you receive source code
or can get it if you want it, that you can change the
software or use pieces of it in new free programs;
and that you know you can do these things.To protect
your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to
surrender the rights. These restrictions translate to
certain responsibilities for you if you distribute copies
of the software, or if you modify it.For example, if you
distribute copies of such a program, whether gratis
or for a fee, you must give the recipients all the rights
that you have. You must make sure that they, too,
receive or can get the source code. And you must
show them these terms so they know their rights.We
protect your rights with two steps: (1) copyright the
software, and (2) offer you this license which gives
you legal permission to copy, distribute and/or modify
the software.
Also, for each author’s protection and ours, we want
to make certain that everyone understands that there
is no warranty for this free software. If the software
is modified by someone else and passed on, we want
its recipients to know that what they have is not the
original, so that any problems introduced by others
will not reflect on the original authors’ reputations.
Finally, any free program is threatened constantly
by software patents. We wish to avoid the danger
that redistributors of a free program will individually
obtain patent licenses, in effect making the program
proprietary. To prevent this, we have made it clear