Cosmos is Legal!

[Vynn]

Currently Cosmos is not supported by Blizzard but its use is allowed.
http://www.blizzard.com/support/wowGM/?id=agm01480p

Now you know, and knowing is half the battle!

EDIT:
The above link is dead.
New link leads to "Malicious UI Modifications"

http://www.blizzard.com/support/wowgm/?id=agm01716p#mum

We claim that Cosmos is not an addon that provides "an unfair advantage in the game over others."

Edited by Sarf.