Who are the core developers behind the Ripple system?
First of all it's important to point out that Ripple (unlike Bitcoin) has been developed by a company, OpenCoin Inc. There is no information about individual developers on ripple.com or opencoin.com. The following information can be found from the Whois of opencoin.com:
Registrant: OpenCoin Inc 268 Bush St #2724 San Francisco, CA 94104 US
That said Ripple is (will be) open source and decentralized, people can write competing clients and the Ripple network could function in the future without OpenCoin Inc.