Is the GitHub Pages product guaranteed to exist in its current form fifteen years from now?
15 years ago, somebody might have bet on a Yahoo! product as something that would obviously be around for a long time.
It’s best not to make long-term plans on giant corporations’ products unless you’re paying them the kind of money that comes with an actual service agreement.
A small VM that you can easily
move to a new host is a better bet than free hosting du jour at $web_giant.
A full virtual server is pretty far down on the list of options I'd consider if I wanted to host-and-forget a little static website for more than a decade. Just to name a few concerns with this approach:
A small VM needs to be periodically updated, both due to changing web standards (e.g. an old TLS version becoming deprecated) and to prevent it from becoming compromised; at some point, an OS upgrade will become necessary; the service provider might deprecate an old VM format and require a migration to something else entirely.
If the author already does all of that, sure, there won't be any or only very little incremental effort. But weren't we talking about the specific risk of the author losing interest (not financial, but in maintenance) in a small pet project?
Now just contrast all of that with uploading one or a handful of HTTP files to a new server and a bit of configuration at the hoster or your domain/DNS provider.
Static web hosters are also plenty and much more economical (in terms of money and server resources) than running your own web server, and for the reasons above, I wouldn't really consider them "less autonomous".
I can’t look at the source right now (on my tablet), but I’m guessing it’s just some static HTML/CSS with a bit of JavaScript? You could throw that up at any web host (free or paid) in a matter of minutes.
15 years ago it might have been Lycos or Geocities, today it might be GitHub Pages or Netlify. I’m not sure about 15 years from now, but if web browsers as we know them are still around then, there will almost certainly be a service that can host a bit of HTML/CSS/JS around too.
15 years ago, somebody might have bet on a Yahoo! product as something that would obviously be around for a long time.
It’s best not to make long-term plans on giant corporations’ products unless you’re paying them the kind of money that comes with an actual service agreement.
A small VM that you can easily move to a new host is a better bet than free hosting du jour at $web_giant.