Namecoin isn't actually a "registrar" in this case, but the canonical blockchain used with Passcard.info. You can think of it as the self-registration alternative. The Namecoin link is definitely a conversion blackhole. This would be a bit better: https://github.com/namesystem/namesystem/wiki/Namecoin

Onename, which has designed Passcard.info, is attempting to standardize the identity protocol by decoupling it from its core identity registration service.

A somewhat fragmented space, here's an example of another blockchain based identity protocol using the id/* namespace on Namecoin: https://nameid.org/?name=domob