The server behind the English editor.
The docs for the editor are here.
The editor itself is here.
How to set up the server
It's actually pretty simple to set up.
Go to the Developer settings page on GitHub.
Click on the OAuth Apps tab.
Click on the New OAuth App button.
Fill in the form. The only tricky part is the Authorization callback URL. Enter something of this form: http://yourserver.com/oauthcallback -- where the yourserver.com part is replaced with the address of your server.
You will get a Client ID and Client Secret on the profile page for the app. Paste those values into config.json and reboot the server. Now it should have a good connection to GitHub.