Using the following apt-get sources.list file, I was able to (finally) download and install KDevelop and all the neccesary packages.

deb http://kde.tdyc.com potato main crypto optional qt1apps
deb http://security.debian.org stable/updates main contrib non-free
deb ftp://ftp.de.debian.org/debian-non-US/ sarge/non-US main
deb ftp://ftp.de.debian.org/debian/ sarge main
deb ftp://ftp.nerim.net/debian-marillat/ testing main
deb http://www.planet-moll.de/debian/ sarge main
deb http://xnv2.xandros.com/2.0/pkg xandros2.0-xn main contrib non-free
deb http://xnv2.xandros.com/2.0/pkg unsupported2.0-xn main contrib non-free
deb ftp://mirror.mcs.anl.gov/pub/debian/ STABLE main
deb ftp://mirrors.kernel.org/debian/ STABLE contrib
deb ftp://debian.savoirfairelinux.net/debian/ STABLE non-free
deb http://spidermonkey.ximian.com/distributions/debian unstable main
deb http://kde.tdyc.com potato main crypto optional qt1apps
deb http://security.debian.org stable/updates main contrib non-free

Note: On my machine, the path to sources.list is /etc/apt/

This is not neccesarily the path on all machines.