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We, the Free Software Foundation, use the GNU General
Public License for most of our software; it applies also to any
other work released this way by its authors.
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 them 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 prevent others from
denying you these rights or asking you to surrender
the rights. Therefore, you have certain responsibilities if
you distribute copies of the software, or if you modify it:
responsibilities to respect the freedom of others.
For example, if you distribute copies of such a program,
whether gratis or for a fee, you must pass on to the recipients
the same freedoms that you received. 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.
Developers that use the GNU GPL protect your rights with
two steps: (1) assert copyright on the software, and (2)
offer you this License giving you legal permission to copy,
distribute and/or modify it.
For the developers’ and authors’ protection, the GPL clearly
explains that there is no warranty for this free software.
For both users’ and authors’ sake, the GPL requires that
modified versions be marked as changed, so that their
problems will not be attributed erroneously to authors of
previous versions.
Some devices are designed to deny users access to install
or run modified versions of the software inside them,
although the manufacturer can do so. This is fundamentally
incompatible with the aim of protecting users’ freedom to
change the software. The systematic pattern of such abuse
occurs in the area of products for individuals to use, which is
precisely where it is most unacceptable. Therefore, we have
designed this version of the GPL to prohibit the practice for
those products. If such problems arise substantially in other
domains, we stand ready to extend this provision to those
domains in future versions of the GPL, as needed to protect
the freedom of users.
Finally, every program is threatened constantly by software
patents. States should not allow patents to restrict
development and use of software on general-purpose
computers, but in those that do, we wish to avoid the special
danger that patents applied to a free program could make it
effectively proprietary. To prevent this, the GPL assures that
patents cannot be used to render the program non-free.
The precise terms and conditions for copying, distribution
and modification follow.
TERMS AND CONDITIONS
0. Definitions.
“This License” refers to version 3 of the GNU General Public
License.
“Copyright” also means copyright-like laws that apply to
other kinds of works, such as semiconductor masks.
“The Program” refers to any copyrightable work licensed
under this License. Each licensee is addressed as “you”.
“Licensees” and “recipients” may be individuals or
organizations.
To “modify” a work means to copy from or adapt all or part
of the work in a fashion requiring copyright permission, other
than the making of an exact copy. The resulting work is
called a “modified version” of the earlier work or a work “based
on” the earlier work.
A “covered work” means either the unmodified Program or a
work based on the Program.
To “propagate” a work means to do anything with it that,
without permission, would make you directly or secondarily
liable for infringement under applicable copyright law, except
executing it on a computer or modifying a private copy.
Propagation includes copying, distribution (with or without
modification), making available to the public, and in some
countries other activities as well.
To “convey” a work means any kind of propagation that
enables other parties to make or receive copies. Mere
interaction with a user through a computer network, with no
transfer of a copy, is not conveying.
An interactive user interface displays “Appropriate Legal
Notices” to the extent that it includes a convenient and
prominently visible feature that (1) displays an appropriate
copyright notice, and (2) tells the user that there is no
warranty for the work (except to the extent that warranties
are provided), that licensees may convey the work under
this License, and how to view a copy of this License. If the
interface presents a list of user commands or options, such
as a menu, a prominent item in the list meets this criterion.
1. Source Code.
The “source code” for a work means the preferred form of
the work for making modifications to it. “Object code” means
any non-source form of a work.
A “Standard Interface” means an interface that either is
an official standard defined by a recognized standards
body, or, in the case of interfaces specified for a particular
programming language, one that is widely used among
developers working in that language.
The “System Libraries” of an executable work include
anything, other than the work as a whole, that (a) is included
in the normal form of packaging a Major Component,
but which is not part of that Major Component, and (b)
serves only to enable use of the work with that Major
Component, or to implement a Standard Interface for which
an implementation is available to the public in source code
form. A “Major Component”, in this context, means a major
essential component (kernel, window system, and so on) of
the specific operating system (if any) on which the executable
work runs, or a compiler used to produce the work, or an
object code interpreter used to run it.
The “Corresponding Source” for a work in object code form
means all the source code needed to generate, install, and (for
an executable work) run the object code and to modify the
work, including scripts to control those activities. However,
it does not include the work’s System Libraries, or general-
purpose tools or generally available free programs which are
used unmodified in performing those activities but which are
not part of the work. For example, Corresponding Source
includes interface definition files associated with source files
for the work, and the source code for shared libraries and
dynamically linked subprograms that the work is specifically
designed to require, such as by intimate data communication
or control flow between those subprograms and other parts
of the work.
The Corresponding Source need not include anything that
users can regenerate automatically from other parts of the
Corresponding Source.
The Corresponding Source for a work in source code form is
that same work.
2. Basic Permissions.
All rights granted under this License are granted for the term
of copyright on the Program, and are irrevocable provided