I looked into this but was only able to duplicate the functionality of the Jive bookmarklet which I personally feel is a bit clunky.
As I mention in the discussion above, my original 'want' was to create a button that allowed the user to share a link/page & comment into any type of Jive submission - Document, Status Update, Blog etc and to also allow them to choose where it was created. The difficulty with this of course is authentication of the user such that the groups/spaces/projects can be requested and returned as choices to the calling code.
Let me look into it some more.
There is the REST API / Ajax, it should allow to do this.