I can't say whether Chuck is still working on TEBE, or plans to, but it does work with the most recent release version of Thunderbird (3.1.14), if you tell it to stop whining about incompatibility.
If you're gutsy, you can edit install.rdf in TEBE's directory in your profile's extensions directory and tell it it's compatible with your version.
If you don't mind having to reset it every time there's an update, and you don't want to risk damaging the .rdf file, you can install the MR Tech Toolkit add-on. That will let you tell Thunderbird to "make compatible" any extension you want. Be warned, that doesn't mean the add-on really is compatible; it just tells Thunderbird that it is. In TEBE's case it is compatible.