Interesting thought experiment is to consider an author who writes a novel in English, but wants to translate it into German.

They have a copyright on the original, and if they hire a human, the human would have a copyright on the translation (which would generally be licensed or transferred back to the author in some way).

If they use an AI for the translation, by the logic here, the translation wouldn't have its own independent copyright, but (based on other long established principles of copyright) it would still be a derived work of the original, so even if this decision holds it would not be legal to make unauthorised AI translations, pirate authorised AI translations, make further translations into other languages (or back to English), etc.

Which seems fairly reasonable! But consider:

If you start with, say, a 90,000 word novel, and ask for a translated novel, you (presumably) have sufficient rights to stop someone making unauthorised copies of the AI translated version.

If you start with a 300 word prompt, and ask for a logo, you (apparently) do not have sufficient rights to stop someone from using it without authorisation.

So some combination of the input (0.3k vs 90k) and the output (logo versus novel) crosses an inflection point between these two extremes, and I think it's interesting to wonder what the boundaries are. Like, in theory you could graph input size versus output complexity, and sketch a frontier between "the author's protected expression survives in the output" and "the author's protected expression does not survive in the output". And I don't have the slightest idea what I think a fair frontier would look like.