Go here: http://packages.debian.org/stable/games/nethack-common

Download the source packages to a directory:
* [nethack_3.4.3-10.1.dsc]
* [nethack_3.4.3.orig.tar.gz]
* [nethack_3.4.3-10.1.diff.gz]

Start scratchbox and cd to that directory, run:

dpkg-source -x nethack_3.4.3-10.1.dsc

cd into the resultant nethack_3.4.3[-10.1] directory (I'm guessing the name here)

Try running this:
dpkg-buildpackage -rfakeroot

If it complains about debhelper version then edit ./debian/compat and change it to a 4, if it complains about other missing deps then you can either add a -f to the above command line to force it (but it may not work) or make sure you install whatever's missing.

Either way, start a new thread to let us know how you get on as this is now very truely off topic. IRC is the other option.