I needed lighttpd’s mod_magnet on Debian Sarge, so I’ve made a backport of Etch’s lighttpd-1.4.13. This backport is just the Etch package compiled on Sarge, without any additional patches. By the way, it depends on some packages from backports.org, so you’ll need to have backports.org on your sources.list.
The packages are here, download and install them with dpkg.