Very generic and free (LGPL) Belief Network Framework in C++ - supports a broad range of knowledge and dependency types for network variables and clusters of variables

Open-source suite of software tools for research and development using graphical models of probability, published by Kansas State University Laboratory for Knowledge Discovery in Databases (KDD)

Kevin Murphy's MATLAB toolbox - supports dynamic BNs, decision networks, many exact and approximate inference algorithms, parameter estimation, and structure learning

Able to learn Bayesian Belief Networks from (possibly incomplete) databases. Algorithm based on the Bound and Collapse estimation method.

Bayesian network laboratory producing a broad set of tools for structure learning, analysis, adaptive questionnaires, and dynamic Bayesian networks

A tool for constructing and testing Bayesian networks.

Bayesian network, simulation and risk analysis software. Supports exact and approximate inference in hybrid and dynamic networks for decision support, diagnosis, statistical learning and prediction applications.