Copyright for libpng source package in Xenial

This is the pre-packaged Debian Linux version of the libpng graphics
library. It was packaged by Philippe Troin 
from sources originally retrieved from http://libpng.org/pub/png/libpng.html

The packaging itself is
copyright (C) 2001 Philippe Troin ,
copyright 2002 Junichi Uekawa ,
copyright 2003 Josselin Mouette  and
copyright 2006-2009 Anibal Monsalve Salazar .
It is licensed under the GNU General Public License v2 or later. On
Debian systems, the GPL is in /usr/share/common-licenses/GPL-2.

Here is the copyright and license for libpng:

  libpng version 1.2.26 - April 2, 2008
  Copyright (c) 1998-2008 Glenn Randers-Pehrson
  (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

  Authors and maintainers:
  libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
  libpng versions 0.97, January 1998, through 1.2.26 - April 2, 2008: Glenn
  See also "Contributing Authors", below.


  COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:

  If you modify libpng you may insert additional notices immediately following
  this sentence.

  libpng versions 1.2.6, August 15, 2004, through 1.2.26, April 2, 2008, are
  Copyright (c) 2004, 2006-2008 Glenn Randers-Pehrson, and are
  distributed according to the same disclaimer and license as libpng-1.2.5
  with the following individual added to the list of Contributing Authors:

     Cosmin Truta

  libpng versions 1.0.7, July 1, 2000, through 1.2.5, October 3, 2002, are
  Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
  distributed according to the same disclaimer and license as libpng-1.0.6
  with the following individuals added to the list of Contributing Authors:

     Simon-Pierre Cadieux
     Eric S. Raymond
     Gilles Vollant

  and with the following additions to the disclaimer:

     There is no warranty against interference with your enjoyment of the
     library or against infringement.  There is no warranty that our
     efforts or the library will fulfill any of your particular purposes
     or needs.  This library is provided with all faults, and the entire
     risk of satisfactory quality, performance, accuracy, and effort is with
     the user.

  libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
  Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson, and are
  distributed according to the same disclaimer and license as libpng-0.96,
  with the following individuals added to the list of Contributing Authors:

     Tom Lane
     Glenn Randers-Pehrson
     Willem van Schaik

  libpng versions 0.89, June 1996, through 0.96, May 1997, are
  Copyright (c) 1996, 1997 Andreas Dilger
  Distributed according to the same disclaimer and license as libpng-0.88,
  with the following individuals added to the list of Contributing Authors:

     John Bowler
     Kevin Bracey
     Sam Bushell
     Magnus Holmgren
     Greg Roelofs
     Tom Tanner

  libpng versions 0.5, May 1995, through 0.88, January 1996, are
  Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.

  For the purposes of this copyright and license, "Contributing Authors"
  is defined as the following set of individuals:

     Andreas Dilger
     Dave Martindale
     Guy Eric Schalnat
     Paul Schmidt
     Tim Wegner

  The PNG Reference Library is supplied "AS IS".  The Contributing Authors
  and Group 42, Inc. disclaim all warranties, expressed or implied,
  including, without limitation, the warranties of merchantability and of
  fitness for any purpose.  The Contributing Authors and Group 42, Inc.
  assume no liability for direct, indirect, incidental, special, exemplary,
  or consequential damages, which may result from the use of the PNG
  Reference Library, even if advised of the possibility of such damage.

  Permission is hereby granted to use, copy, modify, and distribute this
  source code, or portions hereof, for any purpose, without fee, subject
  to the following restrictions:

  1. The origin of this source code must not be misrepresented.

  2. Altered versions must be plainly marked as such and
     must not be misrepresented as being the original source.

  3. This Copyright notice may not be removed or altered from
     any source or altered source distribution.

  The Contributing Authors and Group 42, Inc. specifically permit, without
  fee, and encourage the use of this source code as a component to
  supporting the PNG file format in commercial products.  If you use this
  source code in a product, acknowledgment is not required but would be
  appreciated.