Sorry, but to copy a group to another document is much more complex. Don't use Extend Script for this. Better is to work with Script listener Plugin (AM code) for this.
Or with Extend Script you should loop through the elements of your group and copy part by part. But there are still some things to consider.
What is if you have nested groups or deep nested groups inside of a group?
What is if you have adjustment layers?
What is if you have smart objects?
And sorry for my bad english. I hope you understand nevertheless what I mean.
One thing more:
You've never marked one of your threads as correct - why not?