If you want to play it on mac, you need boot camp. I don't know why it wont let you play mac but I herd that they were able to spread Wizard 101 to Europe. If they can afford to spread it to Europe, they should be able to afford it to work on mac!
i use the program that prospector Zeke mentions to play on my mac, their is a charge to use this program after a 7 day free trial. however it does function well with very few minor problems. boot camp is no longer the only option, however it is the only way to play the 100% error free way until the game is properly ported.