Although I am not a Sharepoint expert, my suggestion was to get the items from the Sharepoint lists in DataTable format with the GetDataTable method
and pass it as source for the grid inside its NeedDataSource handler:
Another possibility to bind the grid is to reference the Sharepoint list items collection directly (if it implements the IList or IEnumerable interfaces) and again supply it as source inside the NeedDataSource handler. See this online resource for more info on the subject:
Thus through the RadGrid instance you should be able to edit MOSS lists as per your requirement.
the Telerik team