Great article… really enjoy reading it :)
So for me is not clear if you are saying that Kafka is an Event Bus implementation using the Event Broker Topology or just another type of Event Bus implementation.
In my opinion Kafka is not using the Broker Topology because for what I remember from playing with Kafka(in last year) it will not notify subscribers. In Kafka Subscribers are Consumers of Topics and they can consume it as many times they want until the event in the Topic goes away and the time that Kafka maintains the Event in the Topic is configurable in days if I am not in mistake.
So Kafka will be more like using Event Sourcing?
Disclaimer: I am learning Event Driven Architecture and Kafka only have played with it once.