Finally it works!!... 😄
BUT I had to move the rs_main.rb from the "\Plugins\as_plugins\as_rubyeditor\snippets"-folder to the "\Plugins"-folder, and then restart SU. At start up it showed the Alertbox "Helle World".
BUT It won't work if I use the playbutton in AS-code editor. It seems like, when using modules, it has to be loaded into SU at startup.
I wonder if there is a way to come around this?
EDITED 1: It can be run directly from the snippet folder with ruby console (then SU requires no restart):
load 'c:\path to the program\Google SketchUp 7\Plugins\as_plugins\as_rubyeditor\snippets\rs_main.rb'
EDITED 2: in rs_main.rb require is changed to load. Then it updates the variables when its changed.
So far so good! Thank you...