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Chapter 12: Appendix
The GNU General Public License (GPL)
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 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 Library 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 that
any patent must be licensed for everyone’s free use or
not licensed at all.
The precise terms and conditions for copying,
distribution and modification follow.
TERMS AND CONDITIONS FOR COPYING,
DISTRIBUTION AND MODIFICATION
0.
This License applies to any program or other work
which contains a notice placed by the copyright holder
saying it may be distributed under the terms of this
General Public License. The “Program”, below, refers to
any such program or work, and a “work based on the
Program” means either the Program or any derivative
work under copyright law: that is to say, a work
containing the Program or a portion of it, either verbatim
or with modifications and/or translated into another
language. (Hereinafter, translation is included without
limitation in the term “modification”.) Each licensee is
addressed as “you”.
Activities other than copying, distribution and
modification are not covered by this License; they are
outside its scope. The act of running the Program is not
restricted, and the output from the Program is covered
only if its contents constitute a work based on the
Program (independent of having been made by running
the Program). Whether that is true depends on what the
Program does.
1. You may copy and distribute verbatim copies of the
Program’s source code as you receive it, in any
medium, provided that you conspicuously and
appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact
all the notices that refer to this License and to the
absence of any warranty; and give any other recipients
of the Program a copy of this License along with the
Program.
You may charge a fee for the physical act of transferring
a copy, and you may at your option offer warranty
protection in exchange for a fee.
2. You may modify your copy or copies of the Program
or any portion of it, thus forming a work based on the
Program, and copy and distribute such modifications or
work under the terms of Section 1 above, provided that
you also meet all of these conditions:
a) You must cause the modified files to carry prominent
notices stating that you changed the files and the date of
any change.
b) You must cause any work that you distribute or
publish, that in whole or in part contains or is derived
from the Program or any part thereof, to be licensed as
a whole at no charge to all third parties under the terms
of this License.
c) If the modified program normally reads commands
interactively when run, you must cause it, when started
running for such interactive use in the most ordinary
way, to print or display an announcement including an
appropriate copyright notice and a notice that there is no
warranty (or else, saying that you provide a warranty)
and that users may redistribute the program under these
conditions, and telling the user how to view a copy of
this License. (Exception: if the Program itself is
interactive but does not normally print such an
announcement, your work based on the Program is not
required to print an announcement.)
These requirements apply to the modified work as a
whole. If identifiable sections of that work are not
derived from the Program, and can be reasonably
considered independent and separate works in
themselves, then this License, and its terms, do not
apply to those sections when you distribute them as
separate works. But when you distribute the same
sections as part of a whole which is a work based on the
Program, the distribution of the whole must be on the
terms of this License, whose permissions for other
licensees extend to the entire whole, and thus to each
and every part regardless of who wrote it.