In the library I read:

/**
 This server side script library implements the tagCloud class
 which is used by the "authorCloud" and "categoryCloud" custom controls.
 
*/
 

Uhm, did you included the correct library? If not can you provide the proper one?

In the readme pdf I also read:

How to re-use control in custom application
1,Copy the following design elements from rating.nsf into your nsf or ntf:
•Custom control: ccRatingCloud – The rating custom control.
•View: xspRatingCloud – the view format used in the rating control.
•JavaScript library (server): RSS - The server side to get the RSS.
•Stylesheet: rating.css – the styling for the control.
•Images: the images from the files section – used to display the rating.

this is also an incorrect reference. Should be xpratingCloud.