A Comprehensive Tutorial \\

\vspace{.1in}

and Guide

}}

\vfill

{\parindent 0in

\begin{tabbing}

Copyright \= \copyright{} 2003--2005, 2008, 2014--2015, 2018 \hspace{1.mm} \=  \kill

Copyright \> \copyright{} 2018 \>  Chestek Legal. \\

Copyright \> \copyright{} 2014--2015 \>  Anthony K. Sebro, Jr. \\

Copyright \= \copyright{} 2014 \> Denver Gingerich. \\

Copyright \= \copyright{} 2003--2007, 2014 \>  Free Software Foundation, Inc. \\

Copyright \> \copyright{} 2008, 2014 \>  Software Freedom Law Center. \\

\end{tabbing}

\vspace{.3in}

The copyright holders grant the freedom to copy, modify, convey,

adapt, and/or redistribute this work (except

Appendices~\ref{GPLv2-full-text}--\ref{AGPLv3-full-text}) under the terms of the Creative Commons

Attribution Share Alike 4.0 International License.  A copy of that license is

entirely separate legal systems.  In short, while GPLv2~\S\S0--3 are the parts

of the license that defend the freedoms of users and programmers,

GPLv2~\S\S4--7 are the parts of the license that keep the playing field clear

so that \S\S~0--3 can do their jobs.

\section{GPLv2~\S4: Termination on Violation}

\label{GPLv2s4}

GPLv2~\S4 is GPLv2's termination clause.  Upon first examination, it seems

strange that a license with the goal of defending users' and programmers'

freedoms for perpetuity in an irrevocable way would have such a clause.

However, upon further examination, the difference between irrevocability

The GPL is irrevocable in the sense that once a copyright holder grants

rights for someone to copy, modify and redistribute the software under terms

of the GPL, they cannot later revoke that grant.  Since the GPL has no

provision allowing the copyright holder to take such a prerogative, the

license is granted as long as the copyright remains in effect.\footnote{In

  the USA, due to unfortunate legislation, the length of copyright is nearly

  perpetual, even though the Constitution forbids perpetual copyright.} The

copyright holders have the right to relicense the same work under different

licenses (see Section~\ref{Proprietary Relicensing} of this tutorial), or to

stop distributing the GPLv2'd version (assuming GPLv2~\S3(b) was never used),

but they may not revoke the rights under GPLv2 already granted.

  permissions under copyright law are automatically restored, notwithstanding

  the strict termination provision in \hyperref[GPLv2s4]{GPLv2~\S4}.

  However, in

  practice, this issue is only salient with regard to \hyperref[Proprietary

    Relicensing]{proprietary relicensing} business models, since other copyright

  holders typically formally restore distributions rights once the only

  remaining compliance issue is ``you lost copyright permission due to

  GPLv2~\S4''.  Therefore, the heated debates, which have raged between

  Jaeger and almost everyone else in the copyleft community for nearly a

  decade, regard an almost moot and wholly esoteric legal detail.}.

\section{GPLv2 Irrevocability}

There are two legal theories why a contributor cannot terminate their license

grant. First is an argument that the text of the GPL prevents it; second is

that a contributor would be estopped from succeeding on an infringement claim

for continued use of the code even if it wasn't removed.

\subsection{The text of the GPLv2}

The GPLv2 have several provisions that, when taken together, can be construed

as an irrevocable license from each contributor. First, the GPLv2 says ``by

\emph{modifying} or distributing the Program (or any work based on the Program), you

indicate your acceptance of this License to do so, and all its terms and

conditions for copying, distributing or modifying the Program or works based