/usr/share/doc/r-cran-rgtk2/copyright is in r-cran-rgtk2 2.20.34-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | This is the Debian GNU/Linux r-omegahat-rgtk2 package of RGtk2, a package which
provides facilities for writing Gtk2 graphical interface from GNU R, and which
was written by Duncan Temple Lang and Michael Lawrence.
This package was created by Dirk Eddelbuettel <edd@debian.org>.
The sources were downloaded from 
	http://www.ggobi.org/RGtk2/
and can also be found on CRAN and its mirrors, e.g. at
	http://cran.r-project.org/src/contrib
The package was renamed from its upstream name 'RGtk2' to 'r-omegahat-rgtk'
 to fit the pattern of CRAN (and non-CRAN) packages for R.
Copyright (C) 2002-2008 Duncan Temple Lang and Michael Lawrence
License: GPL
On a Debian GNU/Linux system, the GPL license is included in the file
/usr/share/common-licenses/GPL.
For reference, the upstream DESCRIPTION file is included below:
   Package: RGtk2
   Version: 2.8.0-0
   Date:    2005/7/29
   Title: R bindings for Gtk 2.0
   Author:  Duncan Temple Lang <duncan@wald.ucdavis.edu> and Michael Lawrence <lawremi@iastate.edu>
   Depends: R (>= 1.2.0)
   Maintainer: Michael Lawrence <lawremi@iastate.edu>
   Description: Facilities in the R language for programming
     graphical interfaces using Gtk, the Gimp Tool Kit.
   License: GPL
   URL:  http://www.omegahat.org/RGtk,  http://www.omegahat.org
         http://www.omegahat.org/bugs
   Packaged: Tue Jan 31 15:48:27 2006; root
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