Yes, you can integrate RadUpload in MOSS 2007, by using the instructions provided in the following pdf document:
You can find more information about the RadControls integration in MOSS in the following page: Integration Guide.
Please, note that we do not have a
MOSS specific version of RadUpload. If you want to use our upload tool
in SharePoint, you will need to write some code that will save the
uploaded files in the MOSS database instead of on disk. You can use the
public SharePoint APIs to add the files in a document library and
provide the additional information ( content type, description, etc.).
If you need additional information about the upload control, you can review the online examples at http://www.telerik.com/demos/aspnet/Upload/Examples/Overview/DefaultCS.aspx and then ask us about a specific feature.
the Telerik team