GNU Free Documentation License
GNU Free Documentation License Version 1.3,
3 November 2008 Copyright © 2000, 2001, 2002, 2007,
2008 Free Software Foundation, Inc.
Everyone is permitted to copy and distribute verbatim
copies of this license document, but changing it is not
The purpose of this License is to make a manual, textbook, or other functional
and useful document “free” in the sense of freedom: to assure everyone the
effective freedom to copy and redistribute it, with or without modifying it, either
commercially or noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not being considered
responsible for modifications made by others.
This License is a kind of “copyleft”, which means that derivative works of the
document must themselves be free in the same sense. It complements the GNU
General Public License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software,
because free software needs free documentation: a free program should come
with manuals providing the same freedoms that the software does. But this
License is not limited to software manuals; it can be used for any textual work,
regardless of subject matter or whether it is published as a printed book. We
recommend this License principally for works whose purpose is instruction or
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that contains
a notice placed by the copyright holder saying it can be distributed under the
terms of this License. Such a notice grants a world-wide, royalty-free license,
unlimited in duration, to use that work under the conditions stated herein. The
“Document”, below, refers to any such manual or work. Any member of the public
is a licensee, and is addressed as “you”. You accept the license if you copy,
modify or distribute the work in a way requiring permission under copyright law.
A “Modified Version” of the Document means any work containing the Document
or a portion of it, either copied verbatim, or with modifications and/or translated
into another language.
A “Secondary Section” is a named appendix or a front-matter section of the
Document that deals exclusively with the relationship of the publishers or authors
of the Document to the Document’s overall subject (or to related matters) and
contains nothing that could fall directly within that overall subject. (Thus, if the
Document is in part a textbook of mathematics, a Secondary Section may not
explain any mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal, commercial,
philosophical, ethical or political position regarding them.
The “Invariant Sections” are certain Secondary Sections whose titles are
designated, as being those of Invariant Sections, in the notice that says that the
Document is released under this License. If a section does not fit the above
definition of Secondary then it is not allowed to be designated as Invariant. The
Document may contain zero Invariant Sections. If the Document does not identify
any Invariant Sections then there are none.
The “Cover Texts” are certain short passages of text that are listed, as Front-
Cover Texts or Back-Cover Texts, in the notice that says that the Document is
released under this License. A Front-Cover Text may be at most 5 words, and a
Back-Cover Text may be at most 25 words.
A “Transparent” copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the general public, that
is suitable for revising the document straightforwardly with generic text editors or
(for images composed of pixels) generic paint programs or (for drawings) some
widely available drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input to text formatters.
A copy made in an otherwise Transparent file format whose markup, or absence
of markup, has been arranged to thwart or discourage subsequent modification
by readers is not Transparent. An image format is not Transparent if used for any
substantial amount of text. A copy that is not “Transparent” is called “Opaque”.
Examples of suitable formats for Transparent copies include plain ASCII without
markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly
available DTD, and standard-conforming simple HTML, PostScript or PDF
designed for human modification. Examples of transparent image formats include
PNG, XCF and JPG. Opaque formats include proprietary formats that can be read
and edited only by proprietary word processors, SGML or XML for which the DTD
and/or processing tools are not generally available, and the machine-generated
HTML, PostScript or PDF produced by some word processors for output
The “Title Page” means, for a printed book, the title page itself, plus such
following pages as are needed to hold, legibly, the material this License requires
to appear in the title page. For works in formats which do not have any title page
as such, “Title Page” means the text near the most prominent appearance of the
work’s title, preceding the beginning of the body of the text.
The “publisher” means any person or entity that distributes copies of the
Document to the public.
A section “Entitled XYZ” means a named subunit of the Document whose title
either is precisely XYZ or contains XYZ in parentheses following text that
translates XYZ in another language. (Here XYZ stands for a specific section name
mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”,
or “History”.) To “Preserve the Title” of such a section when you modify the
Document means that it remains a section “Entitled XYZ” according to this
The Document may include Warranty Disclaimers next to the notice which states
that this License applies to the Document. These Warranty Disclaimers are
considered to be included by reference in this License, but only as regards
disclaiming warranties: any other implication that these Warranty Disclaimers may
have is void and has no effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either commercially
or noncommercially, provided that this License, the copyright notices, and the
license notice saying this License applies to the Document are reproduced in all
copies, and that you add no other conditions whatsoever to those of this License.
You may not use technical measures to obstruct or control the reading or further
copying of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough number of
copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and you
may publicly display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have printed
covers) of the Document, numbering more than 100, and the Document’s license
notice requires Cover Texts, you must enclose the copies in covers that carry,
clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover,
and Back-Cover Texts on the back cover. Both covers must also clearly and
legibly identify you as the publisher of these copies. The front cover must present
the full title with all words of the title equally prominent and visible. You may add
other material on the covers in addition. Copying with changes limited to the
covers, as long as they preserve the title of the Document and satisfy these
conditions, can be treated as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit legibly, you should
put the first ones listed (as many as fit reasonably) on the actual cover, and
continue the rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more
than 100, you must either include a machine-readable Transparent copy along
with each Opaque copy, or state in or with each Opaque copy a computernetwork
location from which the general network-using public has access to
download using public-standard network protocols a complete Transparent copy
of the Document, free of added material. If you use the latter option, you must
take reasonably prudent steps, when you begin distribution of Opaque copies in
quantity, to ensure that this Transparent copy will remain thus accessible at the
stated location until at least one year after the last time you distribute an Opaque
copy (directly or through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of the Document
well before redistributing any large number of copies, to give them a chance to
provide you with an updated version of the Document.
You may copy and distribute a Modified Version of the Document under the
conditions of sections 2 and 3 above, provided that you release the Modified
Version under precisely this License, with the Modified Version filling the role of
the Document, thus licensing distribution and modification of the Modified Version
to whoever possesses a copy of it. In addition, you must do these things in the
* A. Use in the Title Page (and on the covers, if any) a title distinct from that of
the Document, and from those of previous versions (which should, if there were
any, be listed in the History section of the Document). You may use the same title
as a previous version if the original publisher of that version gives permission.
* B. List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified Version, together
with at least five of the principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you from this requirement.
* C. State on the Title page the name of the publisher of the Modified Version,
as the publisher.
* D. Preserve all the copyright notices of the Document.
* E. Add an appropriate copyright notice for your modifications adjacent to the
other copyright notices.
* F. Include, immediately after the copyright notices, a license notice giving the
public permission to use the Modified Version under the terms of this License, in
the form shown in the Addendum below.
* G. Preserve in that license notice the full lists of Invariant Sections and
required Cover Texts given in the Document’s license notice.
* H. Include an unaltered copy of this License.
* I. Preserve the section Entitled “History”, Preserve its Title, and add to it an
item stating at least the title, year, new authors, and publisher of the Modified
Version as given on the Title Page. If there is no section Entitled “History” in the
Document, create one stating the title, year, authors, and publisher of the
Document as given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
* J. Preserve the network location, if any, given in the Document for public
access to a Transparent copy of the Document, and likewise the network
locations given in the Document for previous versions it was based on. These
may be placed in the “History” section. You may omit a network location for a
work that was published at least four years before the Document itself, or if the
original publisher of the version it refers to gives permission.
* K. For any section Entitled “Acknowledgements” or “Dedications”, Preserve
the Title of the section, and preserve in the section all the substance and tone of
each of the contributor acknowledgements and/or dedications given therein.
* L. Preserve all the Invariant Sections of the Document, unaltered in their text
and in their titles. Section numbers or the equivalent are not considered part of
the section titles.
* M. Delete any section Entitled “Endorsements”. Such a section may not be
included in the Modified Version.
* N. Do not retitle any existing section to be Entitled “Endorsements” or to
conflict in title with any Invariant Section.
* O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that
qualify as Secondary Sections and contain no material copied from the
Document, you may at your option designate some or all of these sections as
invariant. To do this, add their titles to the list of Invariant Sections in the Modified
Version’s license notice. These titles must be distinct from any other section titles.
You may add a section Entitled “Endorsements”, provided it contains nothing but
endorsements of your Modified Version by various parties—for example,
statements of peer review or that the text has been approved by an organization
as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover
Texts in the Modified Version. Only one passage of Front-Cover Text and one of
Back-Cover Text may be added by (or through arrangements made by) any one
entity. If the Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity you are
acting on behalf of, you may not add another; but you may replace the old one, on
explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give
permission to use their names for publicity for or to assert or imply endorsement
of any Modified Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified versions,
provided that you include in the combination all of the Invariant Sections of all of
the original documents, unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all their Warranty
The combined work need only contain one copy of this License, and multiple
identical Invariant Sections may be replaced with a single copy. If there are
multiple Invariant Sections with the same name but different contents, make the
title of each such section unique by adding at the end of it, in parentheses, the
name of the original author or publisher of that section if known, or else a unique
number. Make the same adjustment to the section titles in the list of Invariant
Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled “History” in the
various original documents, forming one section Entitled “History”; likewise
combine any sections Entitled “Acknowledgements”, and any sections Entitled
“Dedications”. You must delete all sections Entitled “Endorsements”.
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this License in
the various documents with a single copy that is included in the collection,
provided that you follow the rules of this License for verbatim copying of each of
the documents in all other respects.
You may extract a single document from such a collection, and distribute it
individually under this License, provided you insert a copy of this License into the
extracted document, and follow this License in all other respects regarding
verbatim copying of that document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate and
independent documents or works, in or on a volume of a storage or distribution
medium, is called an “aggregate” if the copyright resulting from the compilation is
not used to limit the legal rights of the compilation’s users beyond what the
individual works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which are not
themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the
Document, then if the Document is less than one half of the entire aggregate, the
Document’s Cover Texts may be placed on covers that bracket the Document
within the aggregate, or the electronic equivalent of covers if the Document is in
electronic form. Otherwise they must appear on printed covers that bracket the
Translation is considered a kind of modification, so you may distribute
translations of the Document under the terms of section 4. Replacing Invariant
Sections with translations requires special permission from their copyright
holders, but you may include translations of some or all Invariant Sections in
addition to the original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the Document, and any
Warranty Disclaimers, provided that you also include the original English version
of this License and the original versions of those notices and disclaimers. In case
of a disagreement between the translation and the original version of this License
or a notice or disclaimer, the original version will prevail.
If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or
“History”, the requirement (section 4) to Preserve its Title (section 1) will typically
require changing the actual title.
You may not copy, modify, sublicense, or distribute the Document except as
expressly provided under this License. Any attempt otherwise to copy, modify,
sublicense, or distribute it is void, and will automatically terminate your rights
under this License.
However, if you cease all violation of this License, then your license from a
particular copyright holder is reinstated (a) provisionally, unless and until the
copyright holder explicitly and finally terminates your license, and (b)
permanently, if the copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is reinstated
permanently if the copyright holder notifies you of the violation by some
reasonable means, this is the first time you have received notice of violation of
this License (for any work) from that copyright holder, and you cure the violation
prior to 30 days after your receipt of the notice.
Termination of your rights under this section does not terminate the licenses of
parties who have received copies or rights from you under this License. If your
rights have been terminated and not permanently reinstated, receipt of a copy of
some or all of the same material does not give you any rights to use it.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of the GNU
Free Documentation 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. See http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the
Document specifies that a particular numbered version of this License “or any
later version” applies to it, you have the option of following the terms and
conditions either of that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If the Document does
not specify a version number of this License, you may choose any version ever
published (not as a draft) by the Free Software Foundation. If the Document
specifies that a proxy can decide which future versions of this License can be
used, that proxy’s public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide
Web server that publishes copyrightable works and also provides prominent
facilities for anybody to edit those works. A public wiki that anybody can edit is an
example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”)
contained in the site means any set of copyrightable works thus published on the
“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license
published by Creative Commons Corporation, a not-for-profit corporation with a
principal place of business in San Francisco, California, as well as future copyleft
versions of that license published by that same organization.
“Incorporate” means to publish or republish a Document, in whole or in part, as
part of another Document.
An MMC is “eligible for relicensing” if it is licensed under this License, and if all
works that were first published under this License somewhere other than this
MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no
cover texts or invariant sections, and (2) were thus incorporated prior to
November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site under
CC-BY-SA on the same site at any time before August 1, 2009, provided the
MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of the
License in the document and put the following copyright and license notices just
after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled “GNU
Free Documentation License”.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the “with … Texts.” line with this:
with the Invariant Sections being LIST THEIR TITLES, with the
Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other combination of
the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend
releasing these examples in parallel under your choice of free software license,
such as the GNU General Public License, to permit their use in free software.
GNU Free Documentation License