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It seems you didn’t snoop around enough 
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Radar uses the Discourse software. At their Github page, it was stated that Discourse is built with:
Ruby on Rails — Our back end API is a Rails app. It responds to requests RESTfully in JSON.
Ember.js — Our front end is an Ember.js app that communicates with the Rails API.
PostgreSQL — Our main data store is in Postgres.
Redis — We use Redis as a cache and for transient data.
9 Likes
Oh. Ok. 
NodeBB almost entirely looks the same.
Edit: Maybe not entirely the same, but similar feel
Don’t even need to snoop past Radar to figure this one out.
I have a dream, like MLK, that one day Radarians will stop asking what tool or framework Radar was built on.
3 Likes
They want their own Radar.