... or 70 years after the author's death right?
I believe you will find that the legal conditions under which something automatically becomes Public Domain varies both on the type of work and the legal region being referenced.
eg.
a. some regal regions use a different number of years as a bench mark.
b. Medium types (Book, Film, Music, etc..) can have different benchmarks.
c. some regal regions automatically placed works created before a set date into the Public Domain.
(in some instances when the creator of the work was still alive!)
d. a work can be still under Copyright (or equivalent) in one regal region while being in the Public Domain in another.
...because there are much better licenses out there for creators who want to release stuff for people to use.
You are aware that those other 'licenses' are generally all legal variations of Copyright?
And that it's generally the legal region's Copyright (and possibly Contract) related laws/regulations that make those 'licenses' enforceable.
If the original artist....
You may of noticed that at no time did I make reference to the original artist or their works, that I was only talking about the topic of Public Domain.
I have no way of knowing exactly how the original artist's works are licenced (Copyright or some other), nor whether they have been added to the Public Domain or not, which is why I didn't mention them in my comment about what Public Domain is.
Ethically is a different matter.... Personally, I believe...
I left it up to others to determine what they personally find ethical and what they choose to believe is right in this situation.