It is based on 2.2.0.GA, and if you download the searchable cache zip file, it contains core 2.2.0.GA.
Does it work at all with 3.0.x? I have an existing 3.0.x application, does that mean I'd have to downgrade to 2.2.x to use SearchableCache?
JBCS 1.0.GA is based on JBoss Cache Core 3.0.1.GA. (see dependencies in the JBCS 1.0.GA pom.xml).
trunk on JBCS is currently using 3.0.2.GA, so either will work.