Don’t know how it works in other country's but here in Belgium (EU country) there is a separate category for royalty's and neighboring rights on the tax reform.
We can report the royalty’s as a natural person separately from other activities we might be doing as a regular employer or as a freelancer who normally sends a bill and invoice to someone.
We actually pay less tax on royalty’s (15%), nice thing about it is that it works with a flat fee for expenses which is up to 50% of what you report (at max up to 35K a year). We only pay tax on the other half. We can go up to 65K a year with this type of arrangement, everything above it should be reported separately.
I assume in other country’s there is some similar arrangements for royalty’s?