Power feeding is feeding a snake on a very rigorous diet in order to get it up to breeding weight as early as possible. Snakes do best on a moderately slow diet (for ball pythons one meal every 1-2 weeks, depending on age, is plenty) and power fed snakes are generally obese and have significantly shortened lifespans. It's a horrible thing to do to an animal.

Based on the pictures he doesn't look underweight or power fed to me.