Seen using latest trunk. I can't install the joey extension from http://joey.labs.mozilla.com/users/getSoftware. I get an error that indicates something about "secure updates are not provided."
You need to change to using a secure update url in the install.rdf. https://joey.labs.mozilla.com/app/webroot/ff/update.rdf should work I imagine.
Joey has been retired. Thanks for participating. http://joey.labs.mozilla.com/