They have been the same for most of history. People could openly copy titles, plots, parts, phrases, etc from prior work. Same for mechanical designs. The only thing preventing them was obscurity (e.g. the inventor trying to make it hidden) not any law or ethical idea that it's bad (there wasn't any). That's how things from math to gears to tunes got better (or changed over time, in the case of art, as better/worse is subjective there).
E.g. globally and historically folk music has been basically taking whatever you want from tunes and songs where everybody does the same with no "permission" asked or needed to be given.
Like 4 verses but want to add a fifth or change some part? Go ahead. Want to play it exactly like you've heard it? Go ahead again.
The idea of "theft" in that regard came in the last 2 or so centuries, and was enforced with artificial legal barriers and new "ethical" concepts that are neither "natural", not present for the vast majority of history (including golden ages of art production).
