The first thing it says under magical beasts:
"Magical Beasts are similar to animals but can have Intelligence scores higher than 2 (in which case the creature knows at least one language, but can’t necessarily speak)"
So it should know at least one language. To say it can't is just mistaken. From what I can tell, given there's no technical way to teach a familiar a language its something that has to be worked out with the GM. Personally I'm of the mind that a familiar should know all the languages its master knows, but I would respect a GM's ruling that said different.