Centralized database? Ummm... How is this possible? According to the plans, Universa will hold not more than 20% of nodes if I'm not mistaken. All other nodes will be from users. Centralized? Nope. The fact that they are licensing nodes does not makes them a centralized system. They use PoA mechanism
Yes, licensing is a sign of centralization. The CEO decides who gets the license. And it doesn't matter how many nodes Universa have officially.
Licensing is not intended to make platform centralized, licensing is a way to make sure that no party can gain too much power.
Basically, we are ok with anybody running the node who fulfill the requirements, as long as they dont collect too much consensus power in single hands.
Unfortunately, there is no algorithm solution that can prevent single hands condition.
Therefore we have to accept that there is no any decentralization possible without such an offline pre-check.