To run the Unity Launcher Editor in Ubuntu 12.04 you need to run the following commands in the Terminal:
sudo apt-get install bzr
bzr branch lp:unity-launcher-editor
cd unity-launcher-editor/
./ule
I’ve noticed that many bloggers are telling you that you should run it by using the “~/unity-launcher-editor/unitylaunchereditor/main.py”, but that file no longer exists.