It seems like the version released to grails central doesn't load the necessary coffee scripts to create/edit page content.
The offending line is in application.js on the master branch there is the line:
//= require_full_tree /spud/admin
but in the multisite_branch it is:
//= require_full_tree .
Changing the one line from /spud/admin to "." fixes it and allows it to load correctly. Not sure how to get a working version of this plugin available for download via grails central.