This a reference to cap'n jazz?

No, in fact this is the first I've heard of Cap'n Jazz.

The name "Cap'n Proto" came from "capabilities and protobuf". The first, never-released version was based on Protobuf serialization. The first public release (way back on April 1, 2013) had its own, all-new serialization.

There's also a pun with it being a "cerealization protocol" (Cap'n Cruch is a well-known brand of cereal).

My first thought too. Glad there are other indie rock folks poking around!