Thanks! I'm still thinking about open sourcing it. I'm also planning on writing a blog post on how things like NPM are implemented in this application.

For now a quick summary of what we use now:

1. Phoenix/Elixir for the API

2. Node for bundling NPM packages

3. Postgres for SQL

4. Redis for caching NPM package metadata

The editor itself is written in React (hah!) and uses styled-components, redux, redux-thunk and react-router@4.0.0 as most used libraries. I code split every optional preference a user may have (like autocomplete, vim or prettify) using webpack 2.

Everything is hosted on Vultr (20$ node).

I'd love to answer more if you have any questions.