Since everyone is having some opinion on what is server and what is a vault, here is mine.
One thing, I hope everyone here would agree is, what, a network of computers/devices is. Based on how these computers communicate with eachother, it is possible to refer to them, as a server, client, peer etc.
Safecoin by definition is much different from the traditional client-server or peer-to-peer architectures, though it uses a lot of features used in traditional architectures.
Now trying to retrofit a term in a new paradigm in to terms defined within older paradigms, is a sure recipe for a disaster. Thus it is best to define new terms for a new paradigm.
To ask if a vault is a server will be a fruitless effort. Though they might have some similar attributes apples are not oranges. But if you take the definition of apple and put much effort you might be able to prove that an orange fits into the same definition, so it is an apple. Would it serve any purpose depends.