ElephantDrive does support NETGEAR ReadyNAS devices under the brand name ReadyNAS Vault.
Yes, you can use ElephantDrive to backup directly from your ReadyNAS device. ElephantDrive works very closely with NETGEAR to provide the customized ReadyNAS Vault solution, which is specifically optimized for integration with the ReadyNAS family of storage devices. If you already have an ElephantDrive account, you can even use the same login credentials to login to the ReadyNAS Vault and backup your ReadyNAS device under the same account.
You can learn more about ReadyNAS Vault here!