JBoss Rules is the supported and branded release of the Drools project and part of the JBoss JEMS product range. Drools is an enhanced Rules Engine implementation, ReteOO, based on Charles Forgy's Rete algorithm tailored for the Java language.
Drools provides for Declarative Programming and is flexible enough to match the semantics of your problem domain with Domain Specific Languages.
Check out the same here.
Open Source Rules Engine - JBoss Rules 3.0 released