Don't be fooled by 3DWorld magazine, the free "full" Terragen on issue 49's cover CD is nothing more than the non-commercial version that you can download from the Terragen website! A quote from their website says:
"And on the cover CD, we'll even be showing you how to create your own Lord of the Rings-style character, with the first of a series of tutorial videos explaining how to model, rig and animate a troll. You'll also find the non-commercial edition of Terragen: a fantastic Mac and PC application for creating photorealistic rendered landscapes."