Douglas has updated the plugin, available here:
https://addons.mozilla.org/firefox/1787/
I have updated his post above.
I am not the original developer, but it appears all that was needed was an update to the Mozilla max version indentifier.
The updated extension works fine for my custom compiled Firefox 3.0a1 alpha development build. I do not use Firefox 2.0, but it should work for it as well.