Ok got it.
What it does is that it uses three iso file as a local repo of software. So it actually doesn't merge them into one iso as you demanded, but it solve some purpose without doing so.
If you want to get rid of CD, DVD to install, then let me share my experience.
I started using Debian as netinstall CD of ~200MB. Then I installed required software.
I stored those .deb files from /var/cache/apt/archives to some /path/myfolder.
Now whenever I have to install anything from /path/myfolder, I use
apt-get -o dir::cache::archives="/path/myfolder" install xyz
The package is installed from local folder rather than network.
So you can just extract all deb packages from DVDs /pool/ folder to your directory, just above.
N.B. This method requires updating from network, DVD packages being older will not work.
Another method :
Here yourpath: whatever root path e.g ~ (home dir.)
*.deb: all packages are put here in main dir.
replace squeeze with distro version name.
i-386 with arch.
apt-ftparchive packages yourpath/debian/pool/main/ |gzip >yourpath/debian/dists/squeeze/main/binary-i386/Packages.gz //In one line.
deb file:yourpath/debian/ squeeze main
in your /etc/apt/sources.list file.
apt-get install program1 program2 ...
This method works without network. So you just need all those DVDs only.