The author has this page hosted from a micro EC2 instance, but they could just as easily serve it from S3, avoiding needing to run any servers / pay for anything except for the bandwidth fees (12c/gb).
Yeah I'm pretty new to the AWS stuff and am still running on my free usage tier. Originally I was running some php on the page, hence the server. Now it's all javascript based so the micro instance isn't needed but I just left it up as it's still free.
Either way, it's a really neat hack.