The author already provides a CDN url. If they are so inclined, creating a memorable url (perhaps even a shortlink) would help with styling quick and dirty projects. I don't think people are doing to be running massive websites using this library.

It is in fact a common business model, known as a CDN (Content Delivery Network). A quick Google search will return many examples.

Most popular libraries (Bootstrap) or fonts are hosted on at least one CDN.

Business being the key term here - this kid is 13, and from what I can tell, doesn't make any money from this. How would it make sense for him to pay to have this available via CDN?

he already provides link to cdn. it seems that the parent didn't like that it was too long.

it could be a http redirect to the cdn

so he will be responsible to maintain the domain name and server for perpetuity, just for short link