It's a currency based on cryptography, let's not try to exclude projects based on random definitions. You want to be more specific, like, it is not censorship-resistant.
Problem with Ripple is creation of new XRPs, they had full control over that.
A decentralized system is a distributed system that still works _when nodes are owned by multiple different (even competing/malicious) parties_.
See the Byzantine Generals Problem[1].