Simple How to Install gOS on Ubuntu . . .

1. Open your sources.list
   $ sudo gedit /etc/apt/sources.list
2. Add new repo line
   deb http://packages.thinkgos.com/gos/ painful main
   deb-src http://packages.thinkgos.com/gos/ painful main
3. Import the key
   wget http://www.thinkgos.com/files/gos_repo_key.asc
   sudo apt-key add gos_repo_key.asc
4. Update your systems
   $ sudo apt-get update
5. Install gOS
   $ sudo apt-get install greenos-desktop xorg
6. And now,  ENLIGHTENMENT sessions should appear in your login manager.

Simple How to Install KDE 4 on Ubuntu . . .

1. Open your sources.list
   $ sudo gedit /etc/apt/sources.list
2. Add new repo line
   deb http://ppa.launchpad.net/kubuntu-members-kde4/ubuntu gutsy main
3. Update your systems
   $ sudo apt-get update
4. Install kde4 system
   $ sudo apt-get install kdebase-workspace kdebase-kde4 kdebase-runtime kde4-core kde4
5. And now, KDE 4 sessions should appear in your login manager.