Currently we only have a MOSS specific version of our RadEditor control. The MOSS editor supports the Safari and FireFox browsers on the Mac platform. You can use it to replace the default MOSS rich text editor, which only works in IE.
Our other controls are also supported in MOSS/WSS v3, but we do not have special builds for SharePoint. You can check the browser requirements for each control in our ASP.NET RadControls suite on this page - http://www.telerik.com/products/aspnet/browser-support.aspx
the Telerik team