Barabas GTK is a GTK interface for Barabas. Since that was probably not very useful, here is a better description.
Barabas GTK is an interface for the Barabas file synchronizing tool. This interface will be the main interface where you can search for files that are stored on the server, and download them locally.
The barabas-gtk client needs the barabas-dbus client, that is not yet public available.