Concurrent Hierarchical State Machine
When using CHSM with Java, you can alternatively specify a statechart using Groovy markup instead of using the CHSM/Java statechart specification language.
Javadoc is included describing the Groovy markup and run-time classes. There are also a few included examples. The source code is also generously commented.
CHSM/Groovy is free software under a BSD-style license. It also happens to be free of cost. (Note that the rest of CHSM is under the GNU General Public License. Please read the licensing details for more information.)
CHSM/Groovy is included as part of the CHSM distribution available from the main CHSM page.