Derek Foreman <derek@signalmarketing.com>
Ben Jansens <xor@orodu.net>
Thomas Schmitt <scdbackup@gmx.net>
Mario Danic <mario.danic@gmail.com>,
Vreixo Formoso <metalpain2002@yahoo.es> 
Steve McIntyre <steve@einval.com>
George Danchev <danchev@spnet.net>

GNU xorriso is a compilation of modules from libburnia-project.org :
xorriso     Copyright (C) 2007-2012 Thomas Schmitt
libisoburn  Copyright (C) 2007-2012 Vreixo Formoso, Thomas Schmitt
libisofs    Copyright (C) 2007-2012 Vreixo Formoso, Mario Danic, Thomas Schmitt
libburn     Copyright (C) 2002-2006 Derek Foreman, Ben Jansens
                          2006-2012 Mario Danic, Thomas Schmitt
Further included is :
libjte      Copyright (C) 2000-2007 Free Software Foundation, Inc.
                          2004-2011 Steve McIntyre
                          2010-2011 George Danchev, Thomas Schmitt

Originally they all are licensed directly or indirectly as GPLv2+.
GNU xorriso is licensed by the following statement:

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License version 3
    or later as published by the Free Software Foundation.

    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA