I wrote and implemented a similar protocol to RPEP in 2013 and have been using it personally, but haven't released it. In my recent search of something similar I found the unfortunately named WAMP (Web Application Messaging Protocol). Despite its goal of being simple and easy to implement, I found the spec complex and bloated. It doesn't stick to being a messaging protocol, also defining routing and brokerage - unnecessarily so in my opinion. I subscribe to the single-responsibility principle, and WAMP seems to violate that. So I wrote up this RPEP spec and want to know what people think about it.
If anyone wants to contribute to RPEP by either making implementations or discussing changes to the spec, please let me know.