I disagree with this completely. Libraries are cached by the Google proxy thing anyway, so as long as you have the correct commit you'll get the correct package even if GitHub goes down or bans the package.
I think version numbers are stupid anyway and people should be versioning based on exact hashes or commit ids, and I think go mod should default to working with exact commits and forget about versions. This would solve many problems.
Including the problem of migrating a package from a github namespace to your own domain namespace. Everything is a breaking change anyway.
But using custom domains is a stupid idea. These people that write these articles live in a fantasy land where everybody is supposed to have their own domain. In practice owning a domain is just an expensive status play conscientious people shouldn't be encouraging the cult of the custom domain.
I also think the article is written in a very poor and confusing way.
I also don't know how Nostr can fix this issue. In fact I think that someone could provide "free golang namespaces for ngit packages" like I do for mine, but more generic. For example, "nostr.technology/npub1.../packagename' could redirect to that package on NIP-34. This just piles up on the GitHub namespacing problems, but because I don't think those are real problems maybe I'll offer this service.