I wrote an Mozilla Persona integration in Clojure with Tom Marble (of the OpenJDK evangelist fame at Sun) and friends at the Clojure.MN meetup a few years ago, here:

https://github.com/tmarble/nongrata.

It was actually a snap to implement. I did most of the coding at it took me maybe a few hours total and I NO idea what I was doing at the time. So if you want to USE Persona or integrate with Mozilla's implementation, there's nothing stopping you.

Writing the full stack of a Persona implementation is a many week to several month job for a half a dozen member team not only for development but from an infosec point of view.