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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.