I am not sure exactly what you mean with your question. If you want to extend (inherit) from the base MOSSRadEditor class, then you need the full featured editor for MOSS. The lite version does not allow you to do this.
If you are not sure how to install the editor in your MOSS web application, then consult the help (.chm file), which comes with the editor download. The same documentation for RadEditor for MOSS lite is also available online - http://www.telerik.com/help/moss/editor/introduction.html
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