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History and License
===================
Sage was initially created by William Stein in 2004--2005, using
Python, IPython, PARI, SWIG, Pyrex, NTL, and GMP. These programs
are all open source and released under the GPL or a GPL-compatible
license.
All Sage releases are released under the GPL. All documentation
is released under the GNU Free Documentation License.
The GNU General Public License
------------------------------
Version 2, June 1991
::
Copyright (C) 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 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.
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.)
2. 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.)
The source code for a work means the preferred form of the work for
making modifications to it. For an executable work, complete source
code means all the source code for all modules it contains, plus
any associated interface definition files, plus the scripts used to
control compilation and installation of the executable. However, as
a special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of
the operating system on which the executable runs, unless that
component itself accompanies the executable.
If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.
4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this
License. However, parties who have received copies, or rights, from
you under this License will not have their licenses terminated so
long as such parties remain in full compliance.
5. You are not required to accept this License, since you have not
signed it. However, nothing else grants you permission to modify or
distribute the Program or its derivative works. These actions are
prohibited by law if you do not accept this License. Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so,
and all its terms and conditions for copying, distributing or
modifying the Program or works based on it.
6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject
to these terms and conditions. You may not impose any further
restrictions on the recipients' exercise of the rights granted
herein. You are not responsible for enforcing compliance by third
parties to this License.
7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent
issues), conditions are imposed on you (whether by court order,
agreement or otherwise) that contradict the conditions of this
License, they do not excuse you from the conditions of this
License. If you cannot distribute so as to satisfy simultaneously
your obligations under this License and any other pertinent
obligations, then as a consequence you may not distribute the
Program at all. For example, if a patent license would not permit
royalty-free redistribution of the Program by all those who receive
copies directly or indirectly through you, then the only way you
could satisfy both it and this License would be to refrain entirely
from distribution of the Program.
If any portion of this section is held invalid or unenforceable
under any particular circumstance, the balance of the section is
intended to apply and the section as a whole is intended to apply
in other circumstances.
It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of
any such claims; this section has the sole purpose of protecting
the integrity of the free software distribution system, which is
implemented by public license practices. Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is
willing to distribute software through any other system and a
licensee cannot impose that choice.
This section is intended to make thoroughly clear what is believed
to be a consequence of the rest of this License.
8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces,
the original copyright holder who places the Program under this
License may add an explicit geographical distribution limitation
excluding those countries, so that distribution is permitted only
in or among countries not thus excluded. In such case, this License
incorporates the limitation as if written in the body of this
License.
9. The Free Software Foundation may publish revised and/or new
versions of the General Public License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the
Program specifies a version number of this License which applies to
it and "any later version", you have the option of following the
terms and conditions either of that version or of any later version
published by the Free Software Foundation. If the Program does not
specify a version number of this License, you may choose any
version ever published by the Free Software Foundation.
10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the
author to ask for permission. For software which is copyrighted by
the Free Software Foundation, write to the Free Software
Foundation; we sometimes make exceptions for this. Our decision
will be guided by the two goals of preserving the free status of
all derivatives of our free software and of promoting the sharing
and reuse of software generally.
**NO WARRANTY**
11. Because the program is licensed free of charge, there is no
warranty for the program, to the extent permitted by applicable
law. Except when otherwise stated in writing the copyright holders
and/or other parties provide the program "as is" without warranty
of any kind, either expressed or implied, including, but not
limited to, the implied warranties of merchantability and fitness
for a particular purpose. The entire risk as to the quality and
performance of the program is with you. Should the program prove
defective, you assume the cost of all necessary servicing, repair
or correction.
12. In no event unless required by applicable law or agreed to in
writing will any copyright holder, or any other party who may
modify and/or redistribute the program as permitted above, be
liable to you for damages, including any general, special,
incidental or consequential damages arising out of the use or
inability to use the program (including but not limited to loss of
data or data being rendered inaccurate or losses sustained by you
or third parties or a failure of the program to operate with any
other programs), even if such holder or other party has been
advised of the possibility of such damages.
**End of Terms and Conditions**
Appendix: How to Apply These Terms to Your New Programs
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make
it free software which everyone can redistribute and change under
these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at
least the "copyright" line and a pointer to where the full notice
is found.
::
one line to give the program's name and a brief idea of what it
does.
Copyright (C) yyyy name of author
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.
Also add information on how to contact you by electronic and paper
mail.
If the program is interactive, make it output a short notice like
this when it starts in an interactive mode::
Gnomovision version 69, Copyright (C) yyyy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type
'show w'.
This is free software, and you are welcome to redistribute it under
certain conditions; type 'show c' for details.
The hypothetical commands show w and show c should show the
appropriate parts of the General Public License. Of course, the
commands you use may be called something other than show w and show
c; they could even be mouse-clicks or menu items--whatever suits
your program.
You should also get your employer (if you work as a programmer) or
your school, if any, to sign a "copyright disclaimer" for the
program, if necessary. Here is a sample; alter the names::
Yoyodyne, Inc., hereby disclaims all copyright interest in the
program
'Gnomovision' (which makes passes at compilers) written by James
Hacker.
signature of Ty Coon, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your
program into proprietary programs. If your program is a subroutine
library, you may consider it more useful to permit linking
proprietary applications with the library. If this is what you want
to do, use the GNU Library General Public License instead of this
License.