The Gtk+ based GUI is still being kept around because ebeast lacks saving, note and track editing.
It's the only real user of the sfidl stubs however, and that in turn majorly holds back porting.
To get out of this legacy maintenance time sink, the Gtk+ code should be removed asap, so development efforts can concentrate on finishing missing functionality in ebeast instead. It might be desirable to at least ensure load/save works properly in ebeast first.
This mess and upcoming regression/usability breakage is the main reason we're still in the 0.x versioning realm btw.