The rules were different at the time Gatsby was published. Its copyright expired 95 years after it was published - 1930 + 95 = 2025.

I was under the impression that the Mickey Mouse Protection Act 1998[1] extended the copyright protection for works retroactively (though already public domain works were excluded).

That being said, I guess the act had precautions to stop it from reducing the copyright protection for edge cases like these?

[1]: https://en.wikipedia.org/wiki/Copyright_Term_Extension_Act

But Nick is not a derivative work; it's something original which references the characters and ideas in The Great Gatsby.

It's pretty crazy that you have to wait until 95 years until the publication of the referenced work to publish something like this.

Is it even about copyright or more about the abstract threat of litigation using copyright as a (baseless) pretext.

Whack, I always naively assumed copyright periods have only ever gotten longer. Good to know The Mouse [1] has precedent behind their legal theory :)

[1] https://en.wikipedia.org/wiki/Copyright_Term_Extension_Act#S...

It was published in 1925 and expired in 2021.