There are talks internally about working towards open-sourcing it, I don't know if/when that'll happen, but it's definitely something we're interested in doing.
We didn't try any of the others, I know that there are quite a few in Golang and Java, but we're pretty python centric at the moment and felt that building it with the tools we have was a better approach.
Lots of companies are shifting from a monolith to microservices and "Chassis" is not a well-known microservice pattern (is it really a pattern...).
Do you have any plan to open source it? Have you ever tried any other solution?