"This software is completely useless to 99.99 percent of users
  out there. It is mostly of use to those interested in audio
  coding research and evaluating codecs. It could theoretically
  be used as a portion of a DVD playback system for unix systems. 
  There are issues with DVD encryption and licensing that need to be
  resolved however."

from the original README file

WWW: http://dara.notbsd.org/~aholtzma/ac3/ac3dec.php