http://fedoraproject.org/wiki/DocBook_Editor_Documentation
Got it running on my system. It requires php, but can deal with "remote files" which is pushes / pulls via HTTP calls. Looks like we can interface it to a webservice.
At the moment Beacon doesn't validate the docbook xml. When you switch to xml view and put in invalid xml (outside tags), it will allow this, and render it as text in the graphical view.
Implementing in https://bugzilla.redhat.com/show_bug.cgi?id=835928 There is interest in merging the work in that bug with the beacon upstream, where they are working on a javascript embeddable version.
Death Star is a WYSIWG editor now.