The so-called copyright violation was that Max Planck had published the same article in 2 journals, which was not unusual at that time, because different journals had different readerships, so publishing in more journals was necessary if you wanted to reach more people.

So supposedly he plagiarized himself.

The second retracted article was even less justifiable, because the modern editors or their automated system had believed that 2 articles were the same, but they were not, they only happened to have the same title.

Never heard this, but very accurate. thanks :)

I notice how the title by Ars Technica is much less baity than Nature: "Why have papers by one of history’s most famous physicists been retracted?" vs "Why did this journal retract two 1940s papers by Max Planck?"