Minimal-desktop-for-ubuntu is a project mainly written in Shell, it's free.
A shell script to build the Ubuntu desktop environment from the ubuntu-minimal install.
GNOME + GDM, KDE + KDM and Flux/Open/Blackbox + XDM are currently supported. A new version is released every six months (in line with Ubuntu's update schedule), with sporadic updates following a release. The scope of these updates is random, but generally rather major.
Ubuntu Minimal Desktop is released under GPL 3.0. (c) Minimal Desktop Team