I do not know if the writers of Fasterfox are working on a update or new version, BUT the reason the old version does not work is very simple.
The .rdf file that is part of the .xpi file that is the actual extension contains the lowest and highest versions of Firefox that the particular extension has been tested on and will run in. In other words the present Fasterfox download will not run in anything past Firefox 2.*.* unless you yourself change the .rdf file.