I would be shocked if GitHub rate limited this new package registry. They're just serving tarballs and static content, and it's a new system so they can fully architect it with scale in mind (i.e. a CDN). They rate limit current repository-related content because they have to dynamically generate most of it in response to requests (I assume they have caching here as well, but not static-file-behind-CDN level caching).
I would be shocked if GitHub rate limited this new package registry. They're just serving tarballs and static content, and it's a new system so they can fully architect it with scale in mind (i.e. a CDN). They rate limit current repository-related content because they have to dynamically generate most of it in response to requests (I assume they have caching here as well, but not static-file-behind-CDN level caching).