> In the court's view, royalties are those items which constitute passive income, such as the compensation paid by a licensee to a licensor for the use of a Page 7 patented invention.
https://www.irs.gov/pub/irs-tege/eotopicd89.pdf
Also, as you say, some royaltie are active incomes. But Passive royalties exist.
> However, if you hold an operating oil, gas, or mineral interest or are in business as a self-employed writer, inventor, artist, etc., report your income and expenses on Schedule C (Form 1040).
https://irs.gov/publications/p525#en_US_2021_publink10002292...
by this measure there may be no such thing as passive income, or at least very few instances of it in this world since just about everything requires you to do something to realize a profit from it. I guess having a rich relative you never knew die and leave you everything is passive, as long as you don't have to go to the will reading or anything.
And if my grandmother had wheels she'd be a wagon. This is obfuscating a useful distinction - labour is stuff you do, spending money in the hope of a return is investment. It's like trying to redefine landlordism as labour because you do occasionally have to do some work.
> Moreover, they can be extended by bank investments or Bitcoin investments, extending their "passive"-side
???
The word everyone is looking for in regard to royalties is not passive or active but deferred income. Writing a book is labour, regardless of word games, and it produces a capital asset - intellectual property - that you can either sell all at once or over a period of time.
> the author doesn't need to promote his books
This is rarely true of books. It sounds like he's found an under-served niche. Once upon a time you didn't have to promote apps in the app store, either.