Rated 4 out of 5 stars
How to make it compatible with FF3:
Extract install.rdf file from the extension file (extensions are simply zip files), then using Notepad (or plain text editor) change 2.0.0.* to 3.* in the file.
now use any zip application to add the modified install.rdf back to extension.
Note: it works fine for me, but may cause things, who knows!