nope, the verifier implementation was always (and still is) open. we recommended against standing up your own verifier since the best practices and processes for securing a verifier weren't known, and the verification process hadn't stabilized. If you have a strong commitment to maintaining your own verifier, you can run one.
You _still_ have to pass verification details back to the Mozilla servers in order to discover whether the login information you're passed is valid, which (a) means that Mozilla can track all of your users and (b) slows everything down.
This is going to put any large site off of relying on it.