بواسطة John Woods (مطوّر) في يونيو 25, 2008 · رابط دائم

You are right... but check the sandbox version... 0.9.15.13.
You must register here on addons.mozilla.org first, then it should show up when you select Show all versions. I did note that in the "long description."

Presently, it is marked as only to work with version 3.0 ~ 3.0.*... but you do satisfy that requirement.