http://ubuntuforums.org/showthread.php?t=803445

This ppa has ns2 (and nam):
Code:

deb http://ppa.launchpad.net/wouterh/ubuntu hardy main
deb-src http://ppa.launchpad.net/wouterh/ubuntu hardy main

Just add it to /etc/apt/sources.list and run:
Code:

sudo apt-get update && sudo apt-get install ns nam