Per his CV he was getting a masters and a PhD at the time. Graduate students often take internships, it's a way of getting funding, extra experience, or just to earn some money while not committing to a full-time position.

Also, I don't think he's the author of this, his name is not in the list of authors. This seems to be a mirror, perhaps with some customization for his class. Probably from his time teaching the intro to Python course (also on his CV) at UCSC.