A blockchain doesn't necessarily have to be currency in the sense of something you use to buy and sell things. It's also a decentralized to store data that shouldn't change unless authorized by an owner (owner here = possessor of a private key). Namecoin is an example - a domain owner can update a name record whenever desired and as long as everyone is using the blockchain a centralized authority cannot prevent the owner from making changes, and a centralized authority cannot make changes the owner doesn't want without the owner's private key.