First off, I want to be absolutely clear that this document has nothing to do with programming languages. It is about how MOZ deals with human languages. This is rather important because MOZ was originally concieved as a way to make a mud that could be interacted with in lojban (See http://www.lojban.org/). The main MOZ code has English and lojban modes.
MOZ is unique, as far as I'm aware, in supporting more than one language at once. Different players can see things in their own language, and their actions (although not their words) will be seen by each player in their own language. So, if a player named 'Foo' opens a door, an English speaking player might see
Foo opens the door.
whereas a lojban speaking player might see
la fus. kargau le vorme
in response to the same action.
Note that the player can have different names in each language (Foo is not proper lojban).
The command one types to open the door will also be different depending on one's language:
open door
versus
se kalri le vorme
Each player can set their preferred language on the fly.