I tested out the Drools IDE in JBDS. I used the Drools icon to create a new Drools project, and ran the DroolsTest class the wizard created as a Java Application. I got the following exception:

java.lang.NoClassDefFoundError: org/antlr/runtime/CharStream

The problem is with defining the "Drools Runtime". As part of the setup for creating a Drools Project for the first time, the user is asked to create a "Drools Runtime". This is new (in the past Drools IDE new which set of jars to use), to be consistent with other tools and allow user to select different Drools Runtimes. The challenge for the user is how to define a Drools Runtime. You can either find the jars in JBDS plugins, explode them into a folder, and point to them, or download Drools engine/expert (in this case I had decided to try jboss-brms-engine-5.ea.zip, since this is the .com version). However when this is unzipped, some jars are in the root of the folder and some are in a lib directory. At least four of the ones in the lib directory are required for runtime (antlr-runtime-3.1.1.jar, core-3.4.2.v_883_R34x.jar, mvel2-2.0.5.jar, xstream-1.3.1.jar), and the jars in a subdirectory are not added to the runtime classpath.

It should be easier for the user to define a Drools Runtime. They should not have to know about which jars to move around. They should just be able to download and unzip.