Justified in removing copyright notices?

["Adam Warner" <lists@consulting.net.nz>]

Hi all,

In 1986/87 John Peterson (now of Haskell fame) wrote a Lisp to Postscript
compiler called PLisp. In 1992 he packaged and distributed it after
posting this 7 April message to comp.lang.lisp and comp.lang.postscript (7
April is in the message ID. GMT time was 6 April):
http://groups.google.com/groups?selm=1992Apr7.014813.1249%40cs.yale.edu

   I made a Common Lisp front end for Postscript called PLisp a few years
   ago.  This translates many common lisp functions to postscript as well
   as manage the environment and many lispisms (&optional and &rest
   arguments, multiple values, macros, ...).  I'm not working on this
   thing anymore but it's available for anyone that wants it.  It's
   available via anonymous ftp in pub/plisp/plisp.tar.Z on
   nebula.cs.yale.edu (128.36.13.1).

The package is archived here:
http://www-2.cs.cmu.edu/afs/cs/project/ai-repository/ai/lang/lisp/code/io/plisp/0.html

The Lisp files were copied to create the tarball that same day, 7 April
1992. 17 of those files contain this copyright notice:

;;; Copyright (c) 1987 John Peterson
;;;   Permission is given to freely modify and distribute this code
;;;   so long as this copyright notice is retained.

John Peterson added a README file to the distribution on 8 April 1992. In
it he exclaims:

   This code is public domain - I don't care what you do with it.  Just
   don't bother me!!

I consider it clear that the only reason these individual copyright
notices remain in the archive is because John Peterson simply copied
over years old files without modifying them. He made his intentions clear
the next day in the README file (perhaps after someone bothered him :-)

Do you concur?

Thanks,
Adam