Faye vs Radar: What are the differences?
Faye: Simple pub/sub messaging for the web. Faye is a set of tools for simple publish-subscribe messaging between web clients. It ships with easy-to-use message routing servers for Node.js and Rack applications, and clients that can be used on the server and in the browser; Radar: High level API and backend for writing web apps that use push messaging. Radar is built on top of engine.io, the next-generation backend for socket.io. It uses Redis for backend storage, though the assumption is that this is only for storing currently active data.
Faye and Radar belong to "Realtime Backend / API" category of the tech stack.
Faye and Radar are both open source tools. It seems that Faye with 4.2K GitHub stars and 386 forks on GitHub has more adoption than Radar with 209 GitHub stars and 35 GitHub forks.