"Proprietary" was bad wording, technically other people can use etcd... I mean to say inflexible & incompatible. Someone suggested supporting Consul 8 years ago (nearly functionally equivalent to Etcd), was requested for years by like a thousand people, never happened. Somebody even submitted a PR I think, but it was quashed. I/O should have been abstracted at the very beginning as loosely-coupled pluggable layers.