They are fully complete, uncrippled, playable and winnable games. Registration of each shareware game brings you a second part. I's second part, and so on. Part 2 of Ultizurk III is called The Mobius Mind. I haven't seen it released as shareware, so you'll have to register UZ III to get it.
Registration is fairly inexpensive, too.
The author gives his name, address and phone number in the documentation. Please contact him for the latest registration info and prices. As I mentioned above, I recommend playing these games in the order shown here.