>...uses long-lived keys that can decrypt all historical traffic (like PGP)...

It is pretty clear from what the article describes that they are not doing some sort of static encryption thing like PGP. They are providing a system that is completely under the control of a central authority. Static encryption would normally give control to the end users at the cost having the users responsible for their own key information. They are not going for any sort of user empowerment here.