' cc-by-sa.tex                                                  -*- LaTeX -*-
%      Tutorial Text for the Detailed Study and Analysis of CC-BY-SA course
%
% Copyright (C) 2014                   Mike Linksvayer

% License: CC-By-SA-4.0

% The copyright holders hereby grant the freedom to copy, modify, convey,
% Adapt, and/or redistribute this work under the terms of the Creative
% Commons Attribution Share Alike 4.0 International License.

% This text 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.

% You should have received a copy of the license with this document in
% a file called 'CC-By-SA-4.0.txt'.  If not, please visit
% https://creativecommons.org/licenses/by-sa/4.0/legalcode to receive
% the license text.

\part{Detailed Analysis of the Creative Commons Attribution-ShareAlike Licenses}

{\parindent 0in
\tutorialpartsplit{``Detailed Analysis of the Creative Commons Attribution-ShareAlike Licenses''}{This part} is: \\
\begin{tabbing}
Copyright \= \copyright{} 2014 \hspace{.1mm} \=  \kill
Copyright \> \copyright{} 2014 \>  Mike Linksvayer
\end{tabbing}


\vspace{.3in}

\begin{center}
Authors of \tutorialpartsplit{``Detailed Analysis of the Creative Commons Attribution-ShareAlike Licenses''}{this part} are: \\
Mike Linksvayer

\vspace{.2in}

Copy editors of this part include: \\
You Please!

\vspace{.2in}


The copyright holders of \tutorialpartsplit{``Detailed Analysis of the GNU GPL and Related Licenses''}{this part} hereby grant the freedom to copy, modify,
convey, Adapt, and/or redistribute this work under the terms of the Creative
Commons Attribution Share Alike 4.0 International License.  A copy of that
license is available at
\url{https://creativecommons.org/licenses/by-sa/4.0/legalcode}.
\end{center}
}

\bigskip

\tutorialpartsplit{This tutorial}{This part of the tutorial} gives a
comprehensive explanation of the most popular free-as-in-freedom copyright
licenses for non-software works, the Creative Commons Attribution-ShareAlike (``CC-BY-SA'', or sometimes just
``BY-SA'') -- with an emphasis on the current version 4.0 (``CC-BY-SA-4.0'').

Upon completion of this part of the tutorial, readers can expect
to have learned the following:

\begin{itemize}

  \item The history and role of copyleft licenses for non-software works.
  \item The differences between the GPL and CC-BY-SA, especially with respect to copyleft policy.
  \item The basic differences between CC-BY-SA versions 1.0, 2.0, 2.5, and 4.0.
  \item An understanding of how CC-BY-SA-4.0 implements copyleft.
  \item Where to find more resources about CC-BY-SA compliance.

\end{itemize}

% FIXME this list should be more aggressive, but material is not yet present

\textbf{WARNING: As of November 2014 this part is brand new, and badly needs review, referencing, expansion, error correction, and more.}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% END OF ABSTRACTS SECTION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% START OF COURSE
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\chapter{Freedom as in Free Culture, Documentation, Education...}

Critiques of copyright's role in concentrating power over and
making culture inaccessible have existed throughout the history
of copyright. Few contemporary arguments about ``copyright in the
digital age'' have not already been made in the 1800s or before.
Though one can find the occasional ad hoc ``anti-copyright'', ``no rights
reserved'', or pro-sharing statement accompanying a publication,
use of formalized public licenses for non-software works seems to
have begun only after the birth of the free software movement and of
widespread internet access among elite populations.

Although they have much older antecedents, contemporary movements
to create, share, and develop policy encouraging ``cultural
commons'', ``open educational resources'', ``open access
scientific publication'' and more, have all come of age in the
last 10-15 years -- after the huge impact of free software was
unmistakable. Additionally, these movements have tended to emphasize
access, with permissions corresponding to the four freedoms of
free software and the use of fully free public licenses as good
but optional.

It's hard not to observe that it seems the free software movement
arose more or less shortly after as it became desirable (due to changes
in the computing industry and software becoming unambiguously subject
to copyright in the United States by 1983), but non-software movements
for free-as-in-freedom knowledge only arose after they became more
or less inevitable, and only begrudgingly at that. Had a free culture
``constructed commons'' movement been successful prior to the birth
of free software, the benefits to computing would have been great --
consider the burdens of privileged access to proprietary culture for
proprietary software through DRM and other mechanisms, toll access
to computer science literature, and development of legal mechanisms
and policy through pioneering trial-and-error.

Alas, counterfactual optimism does not change the present -- but might
embolden our visions of what freedom can be obtained and defended going
forward. Copyleft policy will surely continue to be an important and
controversial factor, so it's worth exploring the current version of
the most popular copyleft license intended for use with non-software
works, Creative Commons Attribution-ShareAlike 4.0 International
(CC-BY-SA-4.0), the focus of this tutorial.


\section{Free Definitions}

When used to filter licenses, the Free Software Definition and
Open Source Definition have nearly identical results. For licenses
primarily intended for non-software works, the Definition of Free
Cultural Works and Open Definition similarly have identical results,
both with each other and with the software definitions which they
imitate. All copyleft licenses for non-software works must be
``free'' and ``open'' per these definitions.

There are various other definitions of ``open access'', ``open
content'', and ``open educational resources'' which are more subject
to interpretation or do not firmly require the equivalent of all four
freedoms of the free software definition. While these definitions
are not pertinent to circumscribing the concept of copyleft -- which
is about enforcing all four freedoms, for everyone. But copyleft
licenses for non-software works are usually considered ``open''
per these other definitions, if they are considered at all.

The open access to scientific literature movement, for example,
seems to have settled into advocacy for non-copyleft free licenses
(CC-BY) on one hand, and acceptance of highly restrictive licenses
or access without other permissions on the other. This creates
practical problems: for example, nearly all scientific literature
either may not be incorporated into Wikipedia (which uses CC-BY-SA)
or may not incorporate material developed on Wikipedia -- both of
which do happen, when the licenses allow it. This tutorial is not
the place to propose solutions, but let this problem be a motivator
for encouraging more widespread understanding of copyleft policy.


\section{Non-software Copylefts}

Copyleft is a compelling concept, so unsurprisingly there have been
many attempts to apply it to non-software works -- starting with use
of GPLv2 for documentation, then occasionally for other texts, and
art in various media. Although the GPL was and is perfectly usable for
any work subject to copyright, several factors were probably important
in preventing it from being the dominant copyleft outside of software:

\begin{itemize}

  \item the GPL is clearly intended first as a software license, thus
requiring some perspective to think of applying to non-software
works;
  \item the FSF's concern is software, and the organization has
not strongly advocated for using the GPL for non-software works;
  \item further due
to the (now previous) importance of its hardcopy publishing business
and desire to retain the ability to take legal action against people
who might modify its statements of opinion, FSF even developed a
non-GPL copyleft license specifically for documentation, the Free
Documentation License (FDL; which ceases to be free and thus is not
a copyleft if its ``invariant sections'' and similar features are
used);
  \item a large cultural gap and lack of population overlap between
free software and other movements has limited knowledge transfer and
abetted reinvention and relearning;
  \item the question of what constitutes source
(``preferred form of the work for making modifications'') for many
non-software works.

\end{itemize}

As a result, several copyleft licenses for non-software works were
developed, even prior to the existence of Creative Commons. These
include the aforementioned FDL (1998), Design Science License (1999),
Open Publication License (1999; like the FDL it has non-free options),
Free Art License (2000), Open Game License (2000; non-free options),
EFF Open Audio License (2001), LinuxTag Green OpenMusic License (2001;
non-free options) and the QING Public License (2002). Additionally
several copyleft licenses intended for hardware designs were proposed
starting in the late 1990s if not sooner (the GPL was then and is now
also commonly used for hardware designs, as is now CC-BY-SA).\footnote{See \url{http://gondwanaland.com/mlog/2012/01/10/open-hardware-licenses-history/}.}

At the end of 2002 Creative Commons launched with 11 1.0 licenses
and a public domain dedication. The 11 licenses consisted of every
non-mutually exclusive combination of at least one of the Attribution
(BY), NoDerivatives (ND), NonCommercial (NC), and ShareAlike
(SA) conditions (ND and SA are mutually exclusive; NC and ND are
non-free). Three of those licenses were free (as was the public domain
dedication), two of them copyleft: CC-SA-1.0 and CC-BY-SA-1.0.

Creative Commons licenses with the BY condition were more popular, so the 5
without (including CC-SA) were not included in version 2.0 of the
licenses. Although CC-SA had some advocates, all who felt
very strongly in favor of free-as-in-freedom, its incompatibility
with CC-BY-SA (meaning had CC-SA been widely used, the copyleft pool
of works would have been further fragmented) and general feeling that
Creative Commons had created too many licenses led copyleft advocates who hoped to
leverage Creative Commons to focus on CC-BY-SA.

Creative Commons began with a small amount of funding and notoriety, but its
predecessors had almost none (FSF and EFF had both, but their entries
were not major focuses of those organizations), so Creative Commons licenses
(copyleft and non-copyleft, free and non-free) quickly came to
dominate the non-software public licensing space. The author of the
Open Publication License came to recommend using Creative Commons licenses, and the
EFF declared version 2.0 of the Open Audio License compatible with
CC-BY-SA and suggested using the latter. Still, at least one copyleft
license for ``creative'' works was released after Creative Commons launched: the
Against DRM License (2006), though it did not achieve wide adoption.
Finally a font-specific copyleft license (SIL Open Font License) was introduced
in 2005 (again the GPL, with a ``font exception'', was and is now
also used for fonts).

Although CC-BY-SA was used for licensing ``databases'' almost from
its launch, and still is, copyleft licenses specifically intended to be
used for databases were proposed starting from the mid-2000s. The most
prominent of those is the Open Database License (ODbL; 2009). As we
can see public software licenses following the subjection of software
to copyright, interest in public licenses for databases followed the
EU database directive mandating ``sui generis database rights'',
which began to be implemented in member state law starting from
1998. How CC-BY-SA versions address databases is covered below.

\subsection{Aside on share-alike non-free therefore non-copylefts}

Many licenses intended for use with non-software works include the
``share-alike'' aspect of copyleft: if adaptations are distributed,
to comply with the license they must be offered under the same terms.
But some (excluding those discussed above) do not grant users the
equivalent of all four software freedoms. Such licenses aren't
true copylefts, as they retain a prominent exclusive property
right aspect for purposes other than enforcing all four freedoms
for everyone. What these licenses create are ``semicommons'' or
mixed private property/commons regimes, as opposed to the commons
created by all free licenses, and protected by copyleft licenses. One
reason non-free public licenses might be common outside software, but
rare for software, is that software more obviously requires ongoing
maintenance.\footnote{For a slightly longer version of this argument, see \href{http://freebeer.fscons.org/freebeer-1.2.pdf#chapter.2}{Free Culture in Relation to Software
Freedom}.} Without control concentrated through copyright assignment
or highly asymmetric contributor license agreements, multi-contributor
maintenance quickly creates an ``anticommons'' -- e.g., nobody has
adequate rights to use commercially.

These non-free share-alike licenses often aggravate freedom and
copyleft advocates as the licenses sound attractive, but typically
are confusing, probably do not help and perhaps stymie the cause of
freedom. There is an argument that non-free licenses offer conservative
artists, publishers, and others the opportunity to take baby steps,
and perhaps support better policy when they realize total control is
not optimal, or to eventually migrate to free licenses. Unfortunately
no rigorous analysis of any of these conjectures. The best that
can be done might be to promote education about and effective use
of free copyleft licenses (as this tutorial aims to do) such that
conjectures about the impact of non-free licenses become about as
interesting as the precise terms of proprietary software EULAs --
demand freedom instead.

In any case, some of these non-free share-alike licenses (also
watch out for aforementioned copyleft licenses with non-free and thus
non-copyleft options) include: Open Content License (1998), Free Music
Public License (2001), LinuxTag Yellow, Red, and Rainbow OpenMusic
Licenses (2001), Open Source Music License (2002), Creative Commons
NonCommercial-ShareAlike and Attribution-NonCommercial-ShareAlike
Licenses (2002), Common Good Public License (2003), and Peer Production
License (2013). CC-BY-NC-SA is by far the most widespread of these,
and has been versioned with the other Creative Commons licenses, through the current
version 4.0 (2013).

\chapter{Creative Commons Attribution-ShareAlike}

The remainder of this tutorial
exclusively concerns the most widespread copyleft license intended
for non-software works, Creative Commons Attribution-ShareAlike

(CC-BY-SA). But, there are actually many CC-BY-SA licenses -- 5
versions (6 if you count version 2.1, a bugfix for a few jurisdiction
``porting'' mistakes), ports to 60 jurisdictions -- 96 distinct
CC-BY-SA licenses in total. After describing CC-BY-SA and how it
differs from the GPL at a high level, we'll have an overview of the
various CC-BY-SA licenses, then a section-by-section walkthrough of
the most current and most clear of them -- CC-BY-SA-4.0.

CC-BY-SA allows anyone to share and adapt licensed material, for
any purpose, subject to providing credit and releasing adaptations
under the same terms. The preceding sentence is a severe abridgement
of the ``human readable'' license summary or ``deed'' provided by
Creative Commons at the canonical URL for one of the CC-BY-SA licenses
-- the actual license or ``legalcode'' is a click away. But this
abridgement, and the longer the summary provided by Creative Commons
are accurate in that they convey CC-BY-SA is a free, copyleft license.

\section{GPL and CC-BY-SA differences}

% FIXME this section ought refernence GPL portion of tutorial extensively

There are several differences between the GPL and CC-BY-SA that are
particularly pertinent to their analysis as copyleft licenses.

The most obvious such difference is that CC-BY-SA does not require
offering works in source form, that is their preferred form for making
modifications. Thus CC-BY-SA makes a huge tradeoff relative to the
GPL -- CC-BY-SA dispenses with a whole class of compliance questions
which are more ambiguous for some creative works than they are for most
software -- but in so doing it can be seen as a much weaker copyleft.

Copyleft is sometimes described as a ``hack'' or ``judo move''
on copyright, but the GPL makes two moves, though it can be hard to
notice they are conceptually different moves, without the contrast
provided by a license like CC-BY-SA, which only substantially makes
one move. The first move is to neutralize copyright restrictions --
adaptations, like the originally licensed work, will effectively
not be private property (of course they are subject to copyright,
but nobody can exercise that copyright to prevent others' use). If
copyright is a privatized regulatory system (it is), the first move
is deregulatory. The second move is regulatory -- the GPL requires
offer of source form, a requirement that would not hold if copyright
disappeared, absent a different regulatory regime which mandated source
revelation (one can imagine such a regime on either ``pragmatic''
grounds, e.g., in the interest of consumer protection, or on the
grounds of enforcing software freedom as a universal human right).

% FIXME analysis of differences in copyleft scope (eg interplay of
% derivative works, modified copies, collections, aggregations, containers) would
% be good here but might be difficult to avoid novel research

CC-BY-SA makes the first move\footnote{See
\url{https://wiki.creativecommons.org/ShareAlike_interpretation}.} but adds
the second in a limited fashion. It does not require offer of preferred
form for modification nor any variation thereof (e.g., the FDL
requires access to a ``transparent copy''). CC-BY-SA does prohibit
distribution with ``effective technical measures'' (i.e., digital
restrictions management or DRM) if doing so limits the freedoms granted
by the license. We can see that this is regulatory because absent
copyright and any regime specifically limiting DRM, such distribution
would be perfectly legal. Note the GPL does not prohibit distribution
with DRM, although its source requirement makes DRM superfluous, and
somewhat analogously, of course GPLv3 carefully regulates distribution
of GPL'd software with locked-down devices -- to put it simply, it
requires keys rather than prohibiting locks. Occasionally a freedom
advocate will question whether CC-BY-SA's DRM prohibition makes
CC-BY-SA a non-free license. Few if any questioners come down on the
side of CC-BY-SA being non-free, perhaps for two reasons: first,
overwhelming dislike of DRM, thus granting the possibility that
CC-BY-SA's approach could be appropriate for a license largely
used for cultural works; second, the DRM prohibition in CC-BY-SA
(and all CC licenses) seems to be mainly expressive -- there are
no known enforcements, despite the ubiquity of DRM in games, apps,
and media which utilize assets under various CC licenses.

Another obvious difference between the GPL and CC-BY-SA is that the
former is primarily intended to be used for software, and the latter
for cultural works (and, with version 4.0, databases). Although those
are the overwhelming majority of uses of each license, there are areas
in which both are used, e.g., for hardware design and interactive
cultural works, where there is not a dominant copyleft practice or
the line between software and non-software is not absolutely clear.

This brings us to the third obvious difference, and provides a reason
to mitigate it: the GPL and CC-BY-SA are not compatible, and have
slightly different compatibility mechanisms. One cannot mix GPL and
CC-BY-SA works in a way that creates a derivative work and comply
with either of them. This could change -- CC-BY-SA-4.0 introduced\footnote{
\url{https://wiki.creativecommons.org/ShareAlike_compatibility}}
the possibility of Creative Commons declaring CC-BY-SA-4.0 one-way
(as a donor) compatible with another copyleft license -- the GPL is
obvious candidate for such compatibility. Discussion is expected to
begin in late 2014, with a decision sometime in 2015. If this one-way
compatibility were to be enacted, one could create an adaptation of
a CC-BY-SA work and release the adaptation under the GPL, but not
vice-versa -- which makes sense given that the GPL is the stronger
copyleft.

The GPL has no externally declared compatibility with other licenses
mechanism (and note no action from the FSF would be required for
CC-BY-SA-4.0 to be made one-way compatible with the GPL). The GPL's
compatibility mechanism for later versions of itself differs from
CC-BY-SA's in two ways: the GPL's is optional, and allows for use
of the licensed work and adaptations under later versions; CC-BY-SA's
is non-optional, but only allows for adaptations under later versions.

Fourth, using slightly different language, the GPL and CC-BY-SA's
coverage of copyright and similar restrictions should be identical for
all intents and purposes (GPL explicitly notes ``semiconductor mask
rights'' and CC-BY-SA-4.0 ``database rights'' but neither excludes
any copyright-like restrictions).  But on patents, the licenses are
rather different. CC-BY-SA-4.0 explicitly does not grant any patent
license, while previous versions were silent. GPLv3 has an explicit
patent license, while GPLv2's patent license is implied (see \ref{gpl-implied-patent-grant}
and \ref{GPLv3-drm} for details). This difference ought give serious pause
to anyone considering use of CC-BY-SA for works potentially subject
to patents, especially any potential licensee if CC-BY-SA licensor
holds such patents. Fortunately Creative Commons has always strongly
advised against using any of its licenses for software, and that
advice is usually heeded; but in the space of hardware designs Creative
Commons has been silent, and unfortunately from a copyleft (i.e., use
mechanisms at disposal to enforce user freedom) perspective, CC-BY-SA
is commonly used (all the more reason to enable one-way compatibility,
allowing such projects to migrate to the stronger copyleft).

The final obvious difference pertinent to copyleft policy between
the GPL and CC-BY-SA is purpose. The GPL's preamble makes it clear
its goal is to guarantee software freedom for all users, and even
without the preamble, it is clear that this is the Free Software
Foundation's driving goal. CC-BY-SA (and other CC licenses) state
no purpose, and (depending on version) are preceded with a disclaimer
and neutral ``considerations for'' licensors and licensees to
think about (the CC0 public domain dedication is somewhat of an
exception; it does have a statement of purpose, but even that has
more of a feel of expressing yes-I-really-mean-to-do-this than a
social mission). Creative Commons has always included elements
of merely offering copyright holders additional choices and of
purposefully creating a commons. While CC-BY-SA (and initially
CC-SA) were just among the 11 non-mutually exclusive combinations
of ``BY'', ``NC'', ``ND'', and ``SA'', freedom advocates
quickly adopted CC-BY-SA as ``the'' copyleft for non-software works
(surpassing previously existing non-software copylefts mentioned
above). Creative Commons has at times recognized the special role of
CC-BY-SA among its licenses, e.g., in a \href{https://wiki.creativecommons.org/CC_Attribution-ShareAlike_Intent}{statement of intent}
regarding the license made in order to assure Wikimedians considering
changing their default license from the FDL to CC-BY-SA that the
latter, including its steward, was acceptably aligned with the
Wikimedia movement (itself probably more directly aligned with software
freedom than any other major non-software commons).

% FIXME possibly explain why purpose might be relevant, eg copyleft
% instrument as totemic expression, norm-setting, idea-spreading

% FIXME possibly mention that CC-BY-SA license text is free (CC0)

There are numerous other differences between the GPL and CC-BY-SA that
are not particularly interesting for copyleft policy, such as the
exact form of attribution and notice, and how license translations
are handled. Many of these have changed over the course of CC-BY-SA
versioning.

\section{CC-BY-SA versions}

%FIXME section ought explain jurisdiction ports

This section gives a brief overview of changes across the main versions
(1.0, 2.0, 2.5, 3.0, and 4.0) of CC-BY-SA, again focused on changes
pertinent to copyleft policy. Creative Commons maintains a \href{https://wiki.creativecommons.org/License_Versions}{page}
detailing all significant changes across versions of all of its CC-BY* licenses,
in many cases linking to detailed discussion of individual changes.

As of late 2014, versions 2.0 (the one called ``Generic''; there are
also 18 jurisdiction ports) and 3.0 (called ``Unported''; there are
also 39 ports) are by far the most widely used. 2.0 solely because it
is the only version that the proprietary web image publishing service
Flickr has ever supported. It hosts 27 million CC-BY-SA-2.0 photos
\footnote{As of November 2014. See \url{https://www.flickr.com/creativecommons/} for counts.} and remains the go-to general
source for free images (though it may eventually be supplanted by
Wikimedia Commons, some new proprietary service, or a federation of
free image sharing sites, perhaps powered by GNU MediaGlobin). 3.0
both because it was the current version far longer (2007-2013) than
any other and because it has been adopted as the default license for
most Wikimedia projects.

However apart from the brief notes on each version, we will focus on
4.0 for a section-by-section walkthrough in the next section, as 4.0
is improved in several ways, including understandability, and should
eventually become the most widespread version, both because 4.0 is
intended to remain the current version for the indefinite and long
future, and it would be reasonable to predict that Wikimedia projects
will make CC-BY-SA-4.0 their default license in 2015 or 2016.

% FIXME subsections might not be the right strcuture or formatting here

\subsection{1.0 (2002-12-16)}
CC-BY-SA-1.0 set the expectation for future
versions. But the most notable copyleft policy feature (apart from
the high level differences with GPLv2, such as not requiring source)
was no measure for compatibility with future versions (nor with the
CC-SA-1.0, also a copyleft license, nor with pre-existing copyleft
licenses such as GPL, FDL, FAL, and others, nor with CC jurisdiction
ports, of which there were 3 for 1.0).

\subsection{2.0 (2004-05-25)}
CC-BY-SA-2.0 made itself compatible with
future versions and CC jurisdiction ports of the same version. Creative
Commons did not version CC-SA, leaving CC-BY-SA-2.0 as ``the'' CC
copyleft license. CC-BY-SA-2.0 also adds the only clarification of
what constitutes a derivative work, making ``synchronization of the
Work in timed-relation with a moving image'' subject to copyleft.

\subsection{2.5 (2005-06-09)}
CC-BY-SA-2.5 makes only one change, to allow
licensor to designate another party to receive attribution. This
does not seem interesting for copyleft policy, but the context of the
change is: it was promoted by the desire to make attribution of mass
collaborations easy (and on the other end of the spectrum, to make it
possible to clearly require giving attribution to a publisher, e.g.,
of a journal). There was a brief experiment in branding CC-BY-SA-2.5
as the ``CC-wiki'' license. This was an early step toward Wikimedia
adopting CC-BY-SA-3.0, four years later.

\subsection{3.0 (2007-02-23)}
CC-BY-SA-3.0 introduced a mechanism for
externally declaring bilateral compatibility with other licenses. This
mechanism to date has not been used for CC-BY-SA-3.0, in part because
another way was found for Wikimedia projects to change their default
license from FDL to CC-BY-SA: the Free Software Foundation released
FDL 1.3, which gave a time-bound permission for mass collaboration
sites to migrate to CC-BY-SA. While not particularly pertinent to
copyleft policy, it's worth noting for anyone wishing to study
old versions in depth that 3.0 is the first version to substantially
alter the text of most of the license, motivated largely by making
the text use less U.S.-centric legal language. The 3.0 text is also
considerably longer than previous versions.

\subsection{4.0 (2013-11-25)}
CC-BY-SA-4.0 added to 3.0's
external compatibility declaration mechanism by allowing one-way
compatibility. After release of CC-BY-SA-4.0 bilateral compatibility
was reached with FAL-1.3. As previously mentioned, one-way
compatibility with GPLv3 will soon be discussed.

4.0 also made a subtle change in that an adaptation may be considered
to be licensed solely under the adapter's license (currently
CC-BY-SA-4.0 or FAL-1.3, in the future potentially GPLv3 or or
a hypothetical CC-BY-SA-5.0). In previous versions licenses were
deemed to ``stack'' -- if a work under CC-BY-SA-2.0 were adapted
and released under CC-BY-SA-3.0, users of the adaptation would
need to comply with both licenses. In practice this is an academic
distinction, as compliance with any compatible license would tend to
mean compliance with the original license. But for a licensee using
a large number of works that wished to be extremely rigorous, this
would be a large burden, for it would mean understanding every license
(including those of jurisdiction ports not in English) in detail.

The new version is also an even more complete rewrite of 3.0 than 3.0
was of previous versions, completing the ``internationalization''
of the license, and actually decreasing in length and increasing
in readability.

Additionally, 4.0 consistently treats database (licensing them
like other copyright-like rights) and moral rights (waiving them to
the extent necessary to exercise granted freedoms) -- in previous
versions some jurisdiction ports treated these differently -- and
tentatively eliminates the need for jurisdiction ports. Official
linguistic translations are underway (Finnish is the first completed)
and no legal ports are planned for.

4.0 is the first version to explicitly exclude a patent (and less
problematically, trademark) license. It also adds two features akin to
those found in GPLv3: waiver of any right licensor may have to enforce
anti-circumvention if DRM is applied to the work, and reinstatement
of rights after termination if non-compliance corrected within 30 days.

Finally, 4.0 streamlines the attribution requirement, possibly of some
advantage to massive long-term collaborations which historically have
found copyleft licenses a good fit.

The 4.0 versioning process was much more extensively researched,
public, and documented than previous CC-BY-SA versionings;
see \url{https://wiki.creativecommons.org/4.0} for the record and
\url{https://wiki.creativecommons.org/Version_4} for a summary of
final decisions.


\section{CC-BY-SA-4.0 International section-by-section}

% FIXME arguably this section ought be the substance of the tutorial, but is very thin and weak now

% FIXME formatted/section-referenced copy of license should be added to license-texts.tex
% and referenced throughout

The best course of action at this juncture would be to read
\url{http://creativecommons.org/licenses/by-sa/4.0/legalcode} -- the entire
text is fairly easy to read, and should be quickly understood if one
has the benefit of study of other public licenses and of copyleft
policy.

The following walk-through will simply call out portions of each
section one may wish to study especially closely due to their
pertinence to copyleft policy issues mentioned above.

% FIXME subsections might not be the right structure or formatting here

\subsection{1 -- Definitions}

The first three definitions -- ``Adapted Material'', ``Adapter's
License'', and ``BY-SA Compatible License'' are crucial to
understanding copyleft scope and compatibility.

\subsection{2 -- Scope}

The license grant is what makes all four freedoms available to
licensees. This section is also where waiver of DRM anti-circumvention
is to be found, also patent and trademark exclusions.

\subsection{3 -- License Conditions}

This section contains the details
of the attribution and share-alike requirements; the latter read
closely with aforementioned definitions describe the copyleft aspect
of CC-BY-SA-4.0.

\subsection{4 -- Sui Generis Database Rights}

This section describes how the previous grant and condition sections
apply in the case of a database subject to sui generis database
rights. This is an opportunity to go down a rabbit-hole of trying to
understand sui generis database rights. Generally, this is a pointless
exercise. You can comply with the license in the same way you would if
the work were subject only to copyright -- and determining whether a
database is subject to copyright and/or sui generis database rights is
another pit of futility. You can license databases under CC-BY-SA-4.0
and use databases subject to the same license as if they were any other
sort of work.

\subsection{5 -- Disclaimer of Warranties and Limitation of Liability}

Unsurprisingly, this section does its best to serve as an ``absolute
disclaimer and waiver of all liability.''

\subsection{6 -- Term and Termination}

This section is similar to GPLv3, but without special provision for
cases in which the licensor wishes to terminate even cured violations.

\subsection{7 -- Other Terms and Conditions}

Though it uses different language, like the GPL, CC-BY-SA-4.0 does
not allow additional restrictions not contained in the license. Unlike
the GPL, CC-BY-SA-4.0 does not have an explicit additional permissions
framework, although effectively a licensor can offer any other terms
if they are the sole copyright holder (the license is non-exclusive),
including the sorts of permissions that would be structured as
additional permissions with the GPL. Creative Commons has sometimes
called offering of separate terms (whether additional permissions or
``proprietary relicensing'') the confusing name ``CC+''; however
where this is encountered at all it is usually in conjunction with one
of the non-free CC licenses. Perhaps CC-BY-SA is not a strong enough
copyleft to sometimes require additional permissions, or be used to
gain commercially valuable asymmetric rights, in contrast with the GPL.

\subsection{8 -- Interpretation}

Nothing surprising here. Note that CC-BY-SA does not ``reduce, limit,
restrict, or impose conditions on any use of the Licensed Material that
could lawfully be made without permission under this Public License.''
This is a point that Creative Commons has always been eager to make
about all of its licenses. GPLv3 also ``acknowledges your rights
of fair use or other equivalent''. This may be a wise strategy,
but should not be viewed as mandatory for any copyleft license --
indeed, the ODbL attempts (somewhat self-contradictorily; it also
acknowledges fair use or other rights to use) make its conditions
apply even for works potentially subject to neither copyright nor
sui generis database rights.


\section{Enforcement}

There are only a small number of court cases involving any Creative
Commons license. Creative Commons lists these and some related cases
at \url{https://wiki.creativecommons.org/Case_Law}.

Only two of those cases concern enforcing the terms of a CC-BY-SA
license (Gerlach v. DVU in Germany, and No. 71036 N. v. Newspaper
in a private Rabbinical tribunal) each hinged on attribution,
not share-alike.

Further research could uncover out of compliance uses being
brought into compliance without lawsuit, however no such
research, nor any hub for conducting such compliance work,
is known. Editors of Wikimedia Commons document some external
uses of Commons-hosted media, including whether user are compliant
with the relevant license for the media (often CC-BY-SA), resulting in a 
\href{https://commons.wikimedia.org/wiki/Category:Files_reused_by_external_parties_out_of_compliance_with_licensing_terms}{category} listing non-compliant uses (which seem to almost exclusively concern attribution).

\section{Compliance Resources}

% FIXME this section is just a stub; ideally there would also be an addition section
% or chapter on CC-BY-SA compliance

Creative Commons has a page on
\href{https://wiki.creativecommons.org/ShareAlike_interpretation}{ShareAlike
interpretation} as well as an extensive Frequently Asked Questions
\href{https://wiki.creativecommons.org/Frequently_Asked_Questions#For_Licensees}{for
licensees} which addresses compliance with the attribution condition.

\href{https://en.wikipedia.org/wiki/Wikipedia:Reusing_Wikipedia_content}{English
Wikipedia}'s and
\href{https://commons.wikimedia.org/wiki/Commons:Reusing_content_outside_Wikimedia}{Wikimedia
Commons}' pages on using material outside of Wikimedia projects provide
valuable information, as the majority of material on those sites is
CC-BY-SA licensed, and their practices are high-profile.

% FIXME there is no section on business use of CC-BY-SA; there probably ought to be 
% as there is one for GPL, though there'd be much less to put.

% =====================================================================
% END OF ATTRIBUTION-SHAREALIKE SECTION
% =====================================================================

%%  LocalWords:  ShareAlike
