To use RadEditor in custom MOSS solutions, you can use the MOSSRadEditor base class. Please note that this a feature of the Standard version only
. With the Lite version, this scenario is not possible.
More information on the subject is available in the documentation, section How-to. Here is a direct link to the online version of the article:http://www.telerik.com/help/radeditormoss/MOSSRadEditor.html
the Telerik team