Probably the most intriguing sub-project out of Étoilé is CoreObject ( http://coreobject.org/ ).
CoreObject is a version-controlled object database for Objective-C that supports powerful undo, semantic merging, and real-time collaborative editing. The page has links to four demonstration videos on YouTube covering branching, tagging, undo, and collaboration.
In essence, all objects are serialized and the container-document is modeled as a database. This is more pervasive than a database like file system.
I sense that the concept of Replicants may somehow potentially be used to implement a more powerful framework than that provided by CoreObject. If so, this could be a “killer” feature unique to BeOS/Haiku.