.. SPDX-FileCopyrightText: © 2019 Alexandros Theodotou <alex@zrythm.org>
.. SPDX-License-Identifier: GFDL-1.3-invariants-or-later
.. This is part of the Zrythm Manual.
   See the file index.rst for copying conditions.

GNU Free Documentation License
==============================

.. code-block:: text

                  GNU Free Documentation License
                   Version 1.3, 3 November 2008


   Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
       <https://fsf.org/>
   Everyone is permitted to copy and distribute verbatim copies
   of this license document, but changing it is not allowed.

  0. PREAMBLE

  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 reference.


  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
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  subject (or to related matters) and contains nothing that could fall
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  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
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  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
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  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
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  processors for output purposes only.

  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",
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  of such a section when you modify the Document means that it remains a
  section "Entitled XYZ" according to this definition.

  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 computer-network 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.


  4. MODIFICATIONS

  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 Modified Version:

  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 Disclaimers.

  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 whole
  aggregate.


  8. TRANSLATION

  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.


  9. TERMINATION

  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
  https://www.gnu.org/licenses/.

  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.

  11. RELICENSING

  "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 MMC site.

  "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.
