It doesn't matter really what 'Mozilla Persona' is. All that matters is that instead of implementing GitHub login, which is a single identity provider, sites should focus on implementing a global solution to login now that a viable one is available.
The general concept here is that the user just needs an email address and a password to login to any site. I'm tired of having to remember a bunch of usernames and passwords, aren't you?
Persona works with any email address, and it's completely decentralized (albeit with a temporary, centralized fallback for bootstrapping)