Microsoft have discontinued support for MOSS (see their official MOSS support lifecycle page) since October 2012. This means that Telerik no longer supports MOSS environments as well.
The Telerik product that was specifically designed for MOSS is RadEditor for MOSS and it is discontinued and it not supported. Its last version is 5.8.16 which is based on the Q2 2012 release of the Telerik UI for ASP.NET AJAX. More information on the matter is available in the RadEditor for MOSS (SharePoint 2007) Discontinued as of Q2 2012 blog post.
The last documentation available for MOSS 2007 is attached to this post.