The jBPM Designer is currently tightly integrated with Drools Guvnor in that it uses its JCR repo as the storage for assets. We have plans to offer a standalone version which will allow to configure your own repository in the next releases. You can use the Designer GUI outside of Guvnor (see here: http://blog.athico.com/2011/04/using-oryx-designer-and-guvnor-in-your.html), or you could use the Guvnor standalone asset editor (see more info here: https://hudson.jboss.org/hudson/job/jBPM/lastSuccessfulBuild/artifact/jbpm-distribution/target/jbpm-5.2.0-SNAPSHOT-docs-build/jbpm-docs/html/ch10.html#d0e3327 - will be available in 2.0 which is just about to be released), but currently you would have to have Guvnor running so that assets can be saved.
Hope this helps.