[wongarsu]

> It’s not copyrightable in the US

That's document is about guidance about works applying to be registered at the Copyright office. Which is a process made largely redundant in 1978 by automatic copyright assignment.

Now the Copyright Office may be of the opinion that copyright doesn't apply, but apart from registrations (or passing new regulations, which they didn't do) they can only give an expert's opinion. To decide how existing laws and regulations apply is the job of the courts.

[wokwokwok]

IANAL, but I’m confident that any assumption that the copyright office is “largely redundant” is not correct.

Of course, you’re welcome to your own opinion, but I urge anyone who believes this to be the case and you know, doing commercial work, to seek legal advice rather than depending on their assumptions about it.

See also -> https://www.copyright.gov/help/faq/faq-general.html#register