From: utzoo!decvax!harpo!seismo!hao!hplabs!sri-unix!cca!csin!cjh
Newsgroups: net.sf-lovers
Title: translation of THE DAY THE EARTH STOOD STILL
Article-I.D.: sri-arpa.218
Posted: Mon Dec 27 08:54:18 1982
Received: Wed Dec 29 01:45:36 1982

In context, it is made very clear that "Klaatu barada nikto" means
something like "Klaatu commands [that] [you] wait/do nothing/don't
harm anything" (look again at the scene where Neal gets these words from
Klaatu, who is specifically worried that Gort will go on a rampage).