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<p>In discussion of the Linux project’s new Code of Conduct, a few
people have suggested that contributors who reject the Code of
Conduct might disrupt Linux licensing in response. This seems
unlikely to most, but to ensure that uncertainty around this issue
casts no shadow over contributions to GPLv2 works, Conservancy
engaged our outside counsel, <a href="https://chesteklegal.com/">Pamela
Chestek</a>, to update the <a
href="https://copyleft.org/guide/"><cite>Copyleft and the GNU
General Public License: A Comprehensive Tutorial and Guide</cite></a>
(called the <cite>Copyleft Guide</cite> for short) on <a
href="https://copyleft.org">copyleft.org</a> to clarify this
issue.</p>
<p> </p>
<p>
Copyleft.org is an initiative that fosters a collaborative
community to share and improve information about copyleft licenses
(especially the GNU General Public License (GPL)) and best
compliance practices for those licenses. It’s primary output is
the Copyleft Guide, an extensive 157 page tutorial on GPL and
other forms of copyleft licensing, available <a
href="https://copyleft.org/guide/">as an online book</a> and <a
href="https://copyleft.org/guide/comprehensive-gpl-guide.pdf">as
a PDF</a>. </p>
<p>Today, a new <a
href="https://copyleft.org/guide/comprehensive-gpl-guidech8.html#x11-540007.4">section
in the Guide</a> explains GPLv2’s safeguards to prevent the very
scenario recently contemplated. In particular, a contributor may
only modify the software and distribute that contribution <strong>if</strong>
they have agreed to the full text of the GPLv2. (“By modifying or
distributing 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 on it.”) Part
of the grant from the contributor is an irrevocable license to
that person’s contribution, provided that the downstream user
complies with the conditions on the license grant. (“Parties who
have received copies, or rights, from you under this License will
not have their licenses terminated so long as such parties remain
in full compliance.”). The contributor is, of course, free to make
no <em>future</em> grants, but they can’t withdraw <em>past</em>
grants. The Guide’s new section also explains how promissory
estoppel is an additional legal safeguard ensuring the withdrawal
of permission will not disrupt the use of those who rely on the
software.</p>
<p>The Copyleft Guide is itself licensed under a copyleft license,
currently CC BY SA 4.0. Experts, lawyers and anyone else
interested in copyleft are welcome to help improve it, via <a
href="https://k.copyleft.org/guide">Conservancy’s Kallithea
instance</a>, or on <a
href="https://github.com/copyleft-org/copyleft-guide">Github</a>.</p>
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