PyModel is an open-source model-based testing framework in Python. Code, documents, and downloads are available:
The initial public release, v 0.80, appeared in January 2010. Version 0.85 adds features that support "passive testing": automatically checking log files (or other traces collected from instrumented systems) against a model. It also adds some improvements to the graphics and a few conveniences and bug fixes.
For details see pymodel/notes/release-0.85.txt at the above site.