Why? So you don't have to place torches while cave exploring. Made for use with donators(as you can bypass some world perms with it). Since 1.2.3 lighting is client-sided, but who says you can't create it using the server?
ml.use - Allows the player to use /ml
/ml - Toggles your Magic Light.
Flowers/Mushrooms/Reeds/Other Crops and etc. get destroyed when you walk over them(it's replacing the grass/sand/farmland with a jack o' lantern). The Jack o' Lantern doesn't get removed when you type /ml.