Web-based process editing is possible using the jBPM5 Designer. The designer is fully integrated into Drools Guvnor, the knowledge repository where you can store all your BPM assets such as of course your BPMN2 processes as well as rules, process images, workitem configurations, and process forms. The Designer can be used to create, view or update BPMN2 processes which are executable in the jBPM5 runtime environment.
One of the main advantages of using a standard like BPMN 2.0 to represent business processes is that it makes interoperability with other tools much easier. Being able to use a web-based modeling tool allows users not to be tied to any particular tooling software and/or systems.
For more information, consult the documentation as well as following blogs and videos:
You can try out the jBPM Web Designer on OpenShift! (note you will not be able to save any created processes).
JBoss AS compatibility:
Where to download: