The $40 is a one time fee like PokerTracker or PokerAce.
You can not rate players with SpadeEye.
It has no scoring system.
You can rate the players in your Pokertracker DB and use the Pokertracker autorating in SpadeEye.
A small guide can be found here:
http://www.spadeit.com/guide.php
Feel free to contact me via ICQ (86080479) or AIM (MrSnoodSpadeEye) for instant help.