The license text does not seem to have updated recently.
It still references to GPL license and also has a copyright date range set from 2007 to 2012.

OpenNMS(R) is Copyright (C) 2007-2012 The OpenNMS Group, Inc. All rights reserved. OpenNMS(R) is a derivative work, containing both original code, included code and modified code that was published under the GNU General Public License. Copyrights for modified and included code are below.

OpenNMS(R) is a registered trademark of The OpenNMS Group, 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 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

For more information contact:
OpenNMS Licensing <license@opennms.org>
http://www.opennms.org/
http://www.opennms.com/