Hello, David Xanatos has a
separate repository, for which you need to be logged into your GitHub account in order to access. Without an account or without being logged in with an account that is eligible, you'll get a 404 (Page not found).
I'm not aware of other ways that is distributed, for users on Patreon for example. Please
send an e-mail to David, so he can enable your access, if you can access it via GitHub, yet.