The move is the second stage of a push to get Twitter into as many languages as humanly possible. I say humanly intentionally as the entire translation process is being open sourced.
Beginning to wonder whether it’s worth keeping you guys updated after every new language is pushed out, but then again, we are supposed to keep you informed.
To see Twitter in German, visit your settings and select “German” from the menu. Oh and keep informed of Twitter’s updates in German by following this account.