I have solved the problem now.
In a newly created environment you have to add the tags
between <ui:composition ...> and <h:form> (sure, the tags have to be closed as usual). Then the pages in rendered correctly and the client side validation works.
So I come to the conclusion that the examples don't work if you copy-paste them to your project what makes it a bit difficult sometimes... :-(
Anyway, if you have this little information, the show cases are really great to learn programming RichFaces.
Best regards, Jochen R.