Those sound like two distinct things to me:

- Copying an interface for the purpose of providing a compatible implementation (what Google allegedly did - although of course part of the debate is whether they also copied any of the implementation)

- Copying parts of the implementation, not for the purpose of compatibility (what faker.js did - in this case, copying constants)

IIRC US copyright law gives very little protection to compilation of non-copyrightable data (look up copyright status of telephone directories). The argument is that it's just public domain factual information bundled together.

The faker libraries are all that -- compilations of mostly non-copyrightable facts.

I'm not saying faker.js did no wrong, just saying if hypothetically a purported copyright owner sued him, they would have a really hard time proving substantial infringement happened given the available precedents.