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.
Thus, it is not the intent of this section to claim rights or contest your
rights to work written entirely by you; rather, the intent is to exercise the
right to control the distribution of derivative or collective works based on
the Program.
In addition, mere aggregation of another work not based on the Program with the
Program (or with a work based on the Program) on a volume of a storage or
distribution medium does not bring the other work under the scope of this
License.
3. You may copy and distribute the Program (or a work based on it, under
Section 2) in object code or executable form under the terms of Sections 1 and
2 above provided that you also do one of the following:
a) Accompany it with the complete corresponding machine-readable source
code, which must be distributed under the terms of Sections 1 and 2 above
on a medium customarily used for software interchange; or,
b) Accompany it with a written offer, valid for at least three years, to
give any third party, for a charge no more than your cost of physically
performing source distribution, a complete machine-readable copy of the
corresponding source code, to be distributed under the terms of Sections 1
and 2 above on a medium customarily used for software interchange; or,
c) Accompany it with the information you received as to the offer to
distribute corresponding source code. (This alternative is allowed only
for noncommercial distribution and only if you received the program in
object code or executable form with such an offer, in accord with
Subsection b above.)
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