FreeGameDev

There is an open source RPG (theoretically multiplayer, but there aren't many players.)
It was developed by Mozilla and is played in the browser.
It makes many things automatically, for example equipping better weapons.

Here it is played:
https://browserquest.io/

Here's the source code (under MPL the Mozilla license).
http://github.com/nenuadrian/BrowserQuest

Greetings
Peter

There are some probably better forks like this one: https://github.com/Kaetram/Kaetram-Open