Because MESS is based on MAME and shares many components with it, it also uses the MAME™ Distribution License. The offical and current version of this license can always be found on MAMEDev and is also mirrored on this page.
The MAME project as a whole is distributed under the terms of the GNU General Public License, version 2 or later (GPL-2.0+), since it contains code made available under multiple GPL-compatible licenses. A great majority of files (over 90% including core files) are under the BSD-3-Clause License and we would encourage new contributors to distribute files under this license.
Please note that MAME is a registered trademark of Nicola Salmoria, and permission is required to use the “MAME” name, logo, or wordmark.
Copyright (C) 1997-2016 MAMEDev and contributors 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 2 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. 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
Please see LICENSE.md for further details.