MDPSim was developed for the First Probabilistic Planning Competition, part of the 4th International Planning Competition (IPC-4) held in 2004. The simulator, with some minor modifications, was used again at the 5th International Planning Competition (IPC-5) in 2006.
The version available here contains some important bug fixes (most importantly, taking care of memory leaks and avoiding execution of invalid plans). The simulator has also been improved so that it better handles problems with quantified goals (for example, the “colored blocksworld” domain). These improvements went into version 2.0, released in September 2005. Unfortunately, that version was never widely distributed, so the organizers of the Second Probabilistic Planning Competition released version 1.23 without knowing about 2.0. The small improvements that went into version 1.23 have been incorporated into the version available here.
As of version 2.2, MDPSim is released under Apache License 2.0. The source code for MDPSim is hosted on GitHub.
Håkan L. S. Younes, Michael L. Littman, David Weissman, and John Asmuth. 2005. The first probabilistic track of the international planning competition. Journal of Artificial Intelligence Research 24: 851–887.
Håkan L. S. Younes and Michael L. Littman. 2004. PPDDL1.0: An extension to PDDL for expressing planning domains with probabilistic effects. Technical Report CMU-CS-04-167, School of Computer Science, Carnegie Mellon University, Pittsburgh, Pennsylvania.