Maintaining copyright notices

[John W. Eaton]

The Octave source files currently contain copyright notices that list 
individual contributors.  I adopted these file-scope copyright notices 
because that is what everyone was doing 30 years ago in the days before 
distributed version control systems.  But now, with many contributors 
and modern version control systems, having these file-scope copyright 
notices causes trouble when we update copyright years or refactor code.

Over time, the file-scope copyright notices may become outdated as new 
contributions are made or code is moved from one file to another. 
Sometimes people contribute significant patches but do not add a line 
claiming copyright.  Other times, people add a copyright notice for 
their contribution but then a later refactoring moves part or all of 
their contribution to another file and the notice is not moved with the 
code.  As a practical matter, moving such notices is difficult -- 
determining what parts are due to a particular contributor requires a 
time-consuming search through the project history.  Even managing the 
yearly update of copyright years is problematic.  We have some 
contributors who are no longer living.  Should we update the copyright 
dates for their contributions when we release new versions?  Probably 
not, but we do still want to claim copyright for the project as a whole.

To minimize the difficulty of maintaining the copyright notices, I would 
like to change Octave's sources to use what is described here


https://softwarefreedom.org/resources/2012/ManagingCopyrightInformation.html

in the section "Maintaining centralized copyright notices":

  The centralized notice approach consolidates all copyright
  notices in a single location, usually a top-level file.
  This file should contain all of the copyright notices
  provided project contributors, unless the contribution was
  clearly insignificant. It may also credit—without a copyright
  notice—anyone who helped with the project but did not
  contribute code or other copyrighted material.

  This approach captures less information about contributions
  within individual files, recognizing that the DVCS is better
  equipped to record those details. As we mentioned before, it
  does have one disadvantage as compared to the file-scope
  approach: if a single file is separated from the distribution,
  the recipient won’t see the contributors’ copyright notices.
  But this can be easily remedied by including a single
  copyright notice in each file’s header, pointing to the
  top-level file:

    Copyright YYYY-YYYY The Octave Project Developers

    See the COPYRIGHT file at the top-level directory
    of this distribution or at https://octave.org/COPYRIGHT.html.

followed by the usual GPL copyright statement.

The COPYRIGHT file would also point to the COPYING file and the AUTHORS 
file.  A draft version of that file is attached.  I created it from 
Mercurial history and old ChangeLog files (for even older changes).  I 
did not generate it directly from the Copyright lines in current source 
files because those lines have things like copyright years updated just 
because we were updating years and those dates have nothing to do with 
the years people actually made contributions.  I'd rather avoid 
propagating the mistake of updating copyright years for people who are 
no longer contributing (possibly because they are dead).

In the future, we will update copyright years for each contributor 
listed in the COPYRIGHT file.  If we are doing that from Mercurial 
history each year, then it seems easier than attempting to do it for 
each source file.

Then the guidelines for updating copyright info each year would be 
something like

  * Update the dates the copyright statements of each file
    so that all source files list the current year.  I believe
    this is justified because the Octave developers are claiming
    copyright for the project as a whole and we publish a version
    during the current year (even without a formal release, the
    sources are published on the web always).

  * Update the dates in the COPYRIGHT file for anyone who
    contributed some change during the year.  It should be
    easy to generate a list of contributors from the hg history
    and fairly easy to match them up with previous contributors
    listed in the COPYRIGHT file.  Should we also try to skip
    trivial changes?  If so, then maybe we should make it
    possible to automate this job by tagging such changes with a
    "[trivial change]" marker in the commit message.

Should the COPYRIGHT file include email addresses with the names?  For 
now, I have them as <...> in the attached copy but the original version 
that I created includes the full addresses.

Additionally, I think it is time to drop the "Author:", "Created:", 
"Adapted-by:" and similar lines that appear in some source files since 
that information is incomplete, tends to become inaccurate over time, 
and is duplicated in the version control system (where it is also most 
likely to be correct).

I'm ready to make these changes prior to the 6.1 release but would like 
to hear from others before proceeding.

jwe

COPYRIGHT.txt
Description: Text document