The musical based on the Christopher Isherwood novel Goodbye to Berlin debuted on Broadway in 1966, immediately striking a chord with the times. Sultry and with plenty of homosexual allusions, Cabaret quickly became a hit. With Kurt Weill’s widow Lotte Lenya as Fräulein Schneider, it even had some legit Berlin flavor. Here in the actual Hauptstadt, director Vincent Paterson (choreographer for Michael Jackson and Madonna) has been staging a German-language version on and off since 2004, and it’s back again for a few weeks this summer. Tonight is the opening night of this run and also serves as a 50th anniversary celebration of the original stage premiere in New York.