Found more license info, snippet from README:

» This directory contains the source distribution for the University of Melbourne
» Mercury compiler, version 0.13.1.
» 
» 	The Mercury implementation is free software, but it is Copyright
» 	(C) 1993-2006 The University of Melbourne.  It is distributed
» 	under the terms of the GNU General Public License.  See the file
» 	COPYING for copying permission.
» 
» 	The Mercury library and runtime (the files in the library and
» 	runtime subdirectories) are distributed under the terms of the
» 	GNU Library General Public License.  See the file COPYING.LIB for
» 	copying permissions for those files.
» 
» 	If those licencing arrangements are not satisfactory, please
» 	contact us!  We are willing to offer alternative arrangements,
» 	if the need should arise.
» 	
» The subdirectory `boehm_gc' contains a slightly modified copy of
» version 6.5 of the conservative garbage collector distributed
» by Hans Boehm:
» 
» 	Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
» 	Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved.
» 	Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
» 	Copyright (c) 1999-2001 by Hewlett-Packard. All rights reserved.
» 
» 	THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
» 	EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
» 
» 	Permission is hereby granted to use or copy this program for any
» 	purpose, provided the above notices are retained on all copies.
» 	Permission to modify the code and to distribute modified code is
» 	granted, provided the above notices are retained, and a notice
» 	that the code was modified is included with the above copyright
» 	notice.
» 
» A few files (config.guess, config.sub) are derived from code that is
» copyright by the Free Software Foundation, Inc, and are distributed
» under the GNU General Public License version 2.
» 
» The program `texi2html' in the `doc' directory is copyright by CERN
» and is distributed under the GNU General Public
» License version 2:
» 
» 	This program is the intellectual property of the European
» 	Laboratory for Particle Physics (known as CERN).  No guarantee
» 	whatsoever is provided by CERN.  No liability whatsoever is
» 	accepted for any loss or damage of any kind resulting from any
» 	defect or inaccuracy in this information or code.
» 
» The files in the `samples' directory are either public domain, or
» distributed under the GNU General Public License.
» 

------------------- The next text applies do a different source package, which we should not want to package, but stays here for reference -------------------

» Some of the files in the `extras' subdirectory (which is now distributed
» separately in the `mercury-extras' package) have fairly restrictive
» copyright licences:  
» 
» 	The `Togl' library in extras/graphics/mtogl/togl.* is copyright by
» 	Brian Paul and Ben Bederson; see the file
» 	extras/graphics/mtogl/LICENSE.TOGL.
» 
» 	The Tk files in extras/graphics/mtogl/tk.* are copyright
» 	by the Regents of the University of California,
» 	Sun Microsystems, Inc., and other parties. 
» 	See the file extras/graphics/mtogl/LICENSE.TK.
» 
» THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.  See the file COPYING.

I will attempt to seek legal advice towards packaging this program (mercury, NOT mercury-extras), when I've the time.