This is currently a Kickstarter project[1] from the people who were originally behind Dark Age of Camelot (DAOC)

They are talking about the in-game UI based on HTML/JS. The game engine will still run natively but they will embed a browser engine for the UI elements. The goal is to allow people to:

1) modify an addon to the UI with familiar technology (even tho LUA is cool!) 2) provide a public api that you can create webapps with. 3) Access a ton of data from the game

So you can interact with your guild mates, trading bazaars, or generate a heat map of the most deathly spots in some webapp without having to load the game at all. Your mods can work on your desktop or in the game.

As a former DAOC player and current developer, I'm in love with this idea. If this interests you, check out their kickstarter page

[1] http://www.kickstarter.com/projects/13861848/camelot-unchained