[omeid2]

Is there any clear line on what is considered a derivative and what is a copy without substantial deviation?

[balls187]

As far as I know, no. It's usually up to a Judge to determine. Per this specific case, the USPS tried to argue something along those lines, but the plaintiff successfully claimed that because the statues face was feminized, it was not a copy, but a derivative.

[omeid2]

That is ingenious. Considering that Mithras is a man, so a feminine version is easy to argue as substantially different.

[xeromal]

In the article, the sculptor claims that he made the statue more feminine.