SPAMfighter Standard is 100% free for home use.
If you want to use SPAMfighter in a professional/educational/governmental environment, you must use SPAMfighter Pro. A 1-year SPAMfighter Pro license costs 29$ (price depends on currency). This is an annual fee, and there is no automatic charge to your credit card! You can also get a discount on higher volume purchases.
After downloading, you can buy SPAMfighter Pro here.