You should be installing it with yum or apt-get.
If you just want the source code this should work:
http://ftp.de.debian.org/debian/pool/main/c/chkrootkit/chkrootkit_0.49.orig.tar.gz
yum install chkrootkit
Setting up Install Process
No package chkrootkit available.
Error: Nothing to do
rpm -ivh http://mirror.us.leaseweb.net/epel/6/i386/epel-release-6-7.noarch.rpm
rpm -ivh http://epel.mirror.freedomvoice.com/5/i386/epel-release-5-4.noarch.rpm
yum -y install chkrootkit