no, the user guide states you should add your custom .class files to BAR, so they are deployed together with the process definition.
http://docs.jboss.org/jbpm/v4/userguide/html_single/#deployingbusinessarchives
The point is, I need my custom classes not because I am using those in my process definition, but because I am saving some serializable variables which need to be deserialized. This deserialization is not possible in another application (admin tool in my case), I am getting "class not found" error.
I presume this functionality is simply not supported and I have to include the .jar with my custom classes to my classpath.
But this is not so nice, because I also deployed those.class files to jbpm database. Do you get my point?