At SE we go by US public domain laws, which typically are a little longer than in other parts of the world. Planet Ebooks are based on Australian public domain laws, so you can’t actually legally download 1984 in the US from them.

(On SE we have a warning that you need to check your own jurisdiction’s public domain laws; you aren’t legally allowed to download Peter and Wendy in the UK for example.)

A little more info on 1984. In Great Britain and most jurisdictions in the world, public domain kicks in 70 years after the death of the author. Orwell died in 1950, so all his corpus entered public domain at the beginning of this year. (In Australia, where these ebooks are hosted, the public domain for this period starts 50 years after the author’s death.)

In the US, the public domain system is different: works enter the public domain 95 years after the initial date of publication of that work. 1984 was published in 1949, so will arrive in the US public domain in 2044. For the next 24 years it’s illegal in the US to download a copy of the book that’s free by virtue of being in the public domain in a different jurisdiction.

This is a bit of an extreme example, as Orwell died just one year after 1984’s publication. In other situations it can work in reverse. For example, Thomas Mann died in 1955, so his works will typically enter the public domain in 2025. However, Der Zauberberg was published in 1924 so is now in the public domain under US law. This (among works by other authors) lead to Gutenberg being blocked in Germany as they weren’t willing to build a geoblocking system.

At the end of the day, if you want to stay legal (big assumption), it’s your responsibility to check PD in the jurisdiction you’re in. Going just by what websites claim is in the PD is not the best idea.

My favorite example of the gap between copyright jurisdictions is P. G. Wodehouse. He died in 1975, but published a lot of work before 1925, including a great many Jeeves and Wooster stories. So in his home country, his work won't be public domain until 2046, but in the U.S. there's plenty of public domain material. There's a similar story with Agatha Christie.

> In the US, the public domain system is different: works enter the public domain 95 years after the initial date of publication of that work.

It's more complicated than that. Works published from 1978 or later (when the 1976 Copyright Act kicked in) is life + 70 years. Works published before then are 95 dates from publication.

> It's more complicated than that. Works published from 1978 or later (when the 1976 Copyright Act kicked in) is life + 70 years. Works published before then are 95 dates from publication.

Actually, it's more complicated than that: for post-1978 works, life + 70 is for works of individual authors, 95 years is for works of corporate authorship.

Actually actually, it's even more complicated than that! Works published between 1925 and 1978 needed to file a copyright extension notice before the 28th anniversary of initial publication or the work fell into public domain.

Copyright law is a maze whose rules have changed numerous times over the decades. Here's a pretty good flowchart for U.S. copyright: https://www.sunsteinlaw.com/copyright-flowchart