This is the Debian prepackaged version of the GNU diffutils package.
GNU `diff' was written by Mike Haertel, David Hayes, Richard Stallman,
Len Tower, and Paul Eggert.  Wayne Davison designed and implemented
the unified output format. GNU `diff3' was written by Randy Smith.
GNU `sdiff' was written by Thomas Lord.  GNU `cmp' was written by
Torbjorn Granlund and David MacKenzie.

The source for this release was obtained from

http://ftp.gnu.org/gnu/diffutils/diffutils-3.0.tar.gz

The Debian .orig.tar.gz is a repackaged version of the above, with
the following changes:

* The doc directory, which contains the manual, has been removed.
* The files `Makefile.in', `configure.ac' and `configure' have been modified
  minimally so that the tarball may be used without any of the auto* tools
  (as it also happens for the unmodified tarball).

Copyright (C) 2010 Free Software Foundation, Inc.

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

On Debian systems, the complete text of the GNU General Public License
may be found in `/usr/share/common-licenses/GPL'.