Types of Freeware

full-featured apps with no advertising and no commercial cousin   ie   Irfanview, 1stPage 2000, GNAT, GRASP
well-featured, non-nagging freeware with commercial cousins   ie   Wordweb, Online Bible, PGPfreeware
well-featured nag-ware demos of commercial apps   ie   Winzip, NJStar Chinese/Japanese word processors, NJStar CJK viewer
ad-driven snoopware ie   Gozilla

note:
freeware like Irfanview is typically an open-source effort or some form of careware - it is left up to you to show your appreciation; some authors actually recommend donating to charity or sending them a postcard!
the rest are typically licensed such that they can only be used non-commercially - if you earn money by using them, then pay for the commercial version