where in this great world wide web could i download the unix core operating system
You could also try Linux from one of several vendors:
Redhat http://www.redhat.com
Suse http://www.suse.com
Mandrake http://www.mandrake.com
Debian http://www.debian.org
Slackware http://www.slackware.org
etc.
Or try one of the BSD's: