Yes it is free. and it's every were nowadays. This site offers "Redhat Linux with CD & Full documentation". see http://www.unix.com

if you are interested and experienced in large downloads there are lots of ftp sites that offers free linux downloads.
checkout:
http://www.redhat.com
http://www.linux-mandrake.com
http://www.debain.org
http://slackware.com

Since you are new to linux/unix Linux-mandrake would be nice one as a staring point. (it's redhat kde top on it)

you can also give a try to BSD UNIX http://www.freebsd.org


HTH