Drools and OpenRules today are two major open sourced business rules products. Our friends from Red Hat created a very powerful BR product and continue to improve it. Both products have well-established customer bases with major corporations using them for years. Both become more and more popular these days - see the recent
Forrester's report. Drools provide one of the best RETE-based rule engine with a very expressive rule language, a powerful CEP engine incorporated in their rules-based environment, and more tools that attract thousands of Java developers worldwide. OpenRules is more oriented to business users and supports a recently introduced the Decision Modeling approach. Additionally we provide
Machine Learning and
Optimization components along with rules-based
Web Questionnairies.
You may try both open source products on your own prototype and decide yourself which one fits your needs better.