BPEL and JPDL are used in differant context. JPDL is a grapgh oriented language developed by jboss. It runs on jbpm engine developed by jboss itself. But BPEL is industry standard. It's purpose is orchestration of webservices. So it is also called bpel-ws. So JPDL and BPEL are used in differant scenarios. JPDL is used to write business logic in graph oriented way. BPEL is used to write the rules for orchestration of many business funtioanalities exposed by partner systems(WEB services).
To run bpel on jboss you have to use jbpm-bpel extension (that is in beta phase)
Oracle provides free modeling tool for bpel. I am not sure wheter eclipse provides it or not.