-- 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}

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

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

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

\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

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.

\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.