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First revision of these two sections.

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Bradley M. Kuhn 2014-03-16 15:11:17 -04:00
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\chapter{A Tale of Two Copyleft Licenses}
While determining the proper methodology and criteria to yield an accurate
count remains difficult, the GPL is generally considered one of the most
widely used Free Software licenses. For most of its history --- for 16 years
from June 1991 to June 2007 --- there was really only one version of the GPL,
version 2.
However, the GPL had both earlier versions before version 2, and, more well
known, a revision to version 3.
\section{Historical Motivations for the General Public License}
The earliest license to grant software freedom was likely the Berkeley
Software Distribution (``BSD'') license. This license is typical of what are
often called lax, highly permissive licenses. Not unlike software in the
public domain, these non-copyleft licenses (usually) grant software freedom
to users, but they do not go to any effort to uphold that software freedom
for users. The so-called ``downstream'' (those who receive the software and
then build new things based on that software) can restrict the software and
distribute further.
The GNU's Not Unix (``GNU'') project, which Richard M.~Stallman (``RMS'')
founded in 1984 to make a complete Unix-compatible operating system
implementation that assured software freedom for all. However, RMS saw that
using a license that gave but did not assure software freedom would be
counter to the goals of the GNU project. RMS invented ``copyleft'' as an
answer to that problem, and began using various copyleft licenses for the
early GNU project programs\footnote{RMS writes more fully about this topic in
his essay entitled simply
\href{http://www.gnu.org/gnu/thegnuproject.html}{\textit{The GNU Project}.
For those who want to hear the story in his own voice,
\href{http://audio-video.gnu.org/audio/}{speech recordings} of his talk,
\textit{The Free Software Movement and the GNU/Linux Operating System}
are also widely available}.
\section{Proto-GPLs And Their Impact}
The earliest copyleft licenses were specific to various GNU programs. For
example, \href{http://www.free-soft.org/gpl_history/emacs_gpl.html}{The Emacs
General Public License} was likely the first copyleft license ever
published. Interesting to note that even this earliest copyleft license
contains a version of the well-known GPL copyleft clause:
\begin{quotation}
You may modify your copy or copies of GNU Emacs \ldots provided that you also
\ldots cause the whole of any work that you distribute or publish, that in
whole or in part contains or is a derivative of GNU Emacs or any part
thereof, to be licensed at no charge to all third parties on terms identical
to those contained in this License Agreement.
\end{quotation}
This simply stated clause is the fundamental innovation of copyleft.
Specifically, copyleft \textit{uses} the copyright holders' controls on
permission to modify the work to add a conditional requirement. Namely,
downstream users may only have permission to modify the work if they pass
along the same permissions on the modified version that came originally to
them.
These original program-specific proto-GPLs give an interesting window into
the central ideas and development of copyleft. In particular, reviewing them
shows how the text of the GPL we know has evolved to address more of the
issues discussed earlier in \S~\ref{software-and-non-copyright}.
\section{The GNU General Public License, Version 1}
\section{The GNU General Public License, Version 2}