This was originally posted over on a Casual Stroll to Mordor but as I’ve gotten a few comments on this I figured I’d post it as well.  I’m glad to see we finally have a blue-name piping up on the forums to clarify what they’re planning to do with the Lua scripting.  Here’s the link to Frelon’s post and you can read the rest of the thread – or his text is below:

We wanted to clarify a few things about the potential implementation of LUA scripting. As it stands right now, the LUA scripting ability is completely controlled by us and its use is limited.
The Framework API, which controls what can and cannot be done, is separated into two main functional areas. The Framework API provides the basic structure of the scripts (classes), UI creation (windows, buttons, images, etc.), and a controlled setting to receive input, events, and actions generated by the game. The Gameplay API provides access to internal gameplay systems. The first pass of the gameplay API includes access to your own character’s vitals, the ability to interface with quickslots, and the methods for interacting with items in your inventory.
So what does this all mean? Right now, given the limitations we have in place, the “plugins” players can create are restricted to the above Gameplay API areas. They can change some of your UI elements, add built in HUDS and allow for things like a travel panel or a single window inventory bag. Our intent is to not allow players to make “plugins” that will give them any kind of advantage over other players. The main idea here is that LUA allows the players the ability to customize their user interface the way they want to.
We are going to handle things very carefully as we move forward; to be very clear, LUA Scripting is still in the early stages of testing and we don’t yet have a date for when the system will go live.

The big things for me are that they’re being careful about what they allow and that you only have access to your own stuff not others, which I assume also means you don’t have access to information on mobs either.  I think this is a great initial plan as it provides good utility and doesn’t open the flood gates to all sorts of other insanity (hopefully).