Game Maker for Mac is the Pro Edition

Game Maker comes in two editions, the Lite Edition and the Pro Edition. Game Maker for Mac only supports the Pro Edition and allows 10 hours of continuous use as an evaluation period before you must purchase a license to use it see http://appstore.yoyogames.com/gm4mac

Continuous use means that while you are using Game Maker the clock is ticking down from 10 hours, if you are not using Game Maker the clock is not ticking - so you can download it and try it for an hour and then leave it for a month, you will have only used an hour of the 10 hours.

Registering Game Maker for the Mac

To register Game Maker for the Mac you need to purchase a license key from http://appstore.yoyogames.com/gm4mac, once the purchase has been made you will receive an email with the license key, you MUST be connected to the internet to activate the license.

Just press the 'Enter License Key' button

Then enter the license key along with the email address (to which the license key was sent).