This is nothing new. It's just an explanation and instructions for running QuickPWN. Jailbreaking does void the warranty, but as long as you restore to factory settings (remove the jailbreak) before going to the Apple Store, you'll be fine.
All you have to do is restore before you bring it in. Something was wrong with my iPhone so i had to bring it to the Apple store. i restored it and brought it in. they hooked it up to their computer did what they had to do and gave it back to me without even noticing it. i re-jb when i got home and everythings fine