Originally Posted by
YojimboM
ACT (if that's what you mean by "overlay") reads network packets, entity lists, and combat log files. It's a "utility" that "interacts" with the game by scraping logs and packets, basically. So, against the TOS. Oh, and you can use plugins in ACT to automate some things, too. It actually does a lot of things besides showing you how much DPS you do, you can have it notify you of hunt mobs within your draw distance, it can track movements of your party and enemies in a fight, etc. It's great and luckily gets turned a blind eye on.