The first kdm theme was created by Petter Reinholdtsen based on the
kdm theme in kubuntu and is licensed under the GNU General Public License. 

Based on the existent kdm and gdm themes, in combination with the
oxygen-air theme (GPL 2008 Xavier Araque) and a new background image
from the Debian moreblue-orbit theme, a refurbished theme was created
by Andreas B. Mundt (GPL 2010).

Wheezy version (based on joy theme) by Wolfgang Schweer (GPLv2+, 2013).
background.svg is a copy of debian-edu-wallpaper02_1600x1200.svg by 
Christoph Muetze.

Resources:
   http://docs.kde.org/stable/en/kdebase-workspace/kdm/kdm-themes.html
   http://developer.skolelinux.no/~vb/logo/

   For further improvements:
   http://wiki.debian.org/DebianDesktopArtworkLenny
   http://wiki.debian.org/DebianDesktopArtworkSqueeze 
