Rated 5 out of 5 stars

by DerAlb on Sept. 8, 2008 ·

You don't need a tool to make it work with FF3.01. Download the xpi file, rename it to zip, open it. Then open the included file install.rdf and change the maximum version entry for Firefox to 3.0.something.*.
Overwrite the existing version, rename zip to xpi and install. Worked for me!