You don't have to register to play Knoword, but you can register if you want to. Registering for Knoword gives you the option to keep track of your game statistics. Registered users can also earn badges based on their performances.
Applications for EducationIn the few games that I played I noticed that Knoword is probably best suited to use by students in middle school and high school. I think many of the words would be too difficult for elementary school students and they could end up frustrated with the game. For middle school and high school students though Knoword could be a fun way to refresh their memories of words they already know and add new words to their vocabularies.