The digium site is not properly redirecting to the asterisk.org site.
The file it downloads is just a directory listing of the site instead of the actual sound files.
The correct link is: http://downloads.asterisk.org/pub/telephony/sounds/releases
Edit the Makefile in the ASL-Asterisk/asterisk/sounds directory.
Change the SOUNDS_URL line to point to the above URL
(thanks to Mike N5ZR for the above info)