To classify the level of support that a BPMN software tool provides, the BPMN standard defines the "conformance classes" as follows:
Process Modeling Conformance: This class includes the BPMN core elements, process, collaboration, and conversation diagrams. It defines subclasses that contain a limited set of visual elements (descriptive), an extended set of modeling elements (analytical), and modeling elements that are required to model executable processes (common executable).
jBPM supports a great part of the Common Executable class, with additional extensions. Please check Chapter 6, Core Architecture, of the jBPM 6.2 user guide for insights into the topic.