While the film includes the notices "MCMLXIII BY UNIVERSAL PICTURES COMPANY, INC" and "STANLEY DONEN FILMS, INC. ALL RIGHTS RESERVED" - it does not include the word, symbol or abbreviation for Copyright. Before 1978, that kind of omission was enough. The film went into public domain immediately upon release in 1963. The Henry Mancini score is still copyrighted if you use it outside the context of the movie.

An interesting case of measuring the spirit of the law against its letter. It seems very unlikely that the omission of copyright language was anything but accidental, but clerical error wasn't a defense, at least before 1978.