Under RHEL 4, I use a repository I found a while ago along with a wonderful package manager. Apt blows Yum out of the water and should immediately replace it.
The many features just makes it a must have for any distribution that supports it, and if it doesn't, they need to get their priorities straight.
I failed to find an installation source for RHEL 4 in your tutorial, just 3. So, I will tell anyone who needs it to find it at the link at the bottom of this reply.
Oh, just make sure you get a good package manager. It's just as important as getting apt itself. I also left a link to get the manager I use, Synaptic.
For apt RHEL X (and Fedora X):
I have written a tutorial about apt on rpm-based distributions.
In this short tutorial I will show how to install and use Debian's package manager apt on various rpm-based distributions like Fedora, Mandrake (or Mandriva, they changed their name...), RedHat, SUSE, and Yellow Dog Linux. apt for rpm is also known as apt4rpm, or aptrpm.
This tutorial is split into two parts: in the first I will demonstrate how to install and use apt based on an example (apt on SUSE 9.2), and in the second part I will give you an overview of the packages to install and the package repositories for each distribution mentioned above.