I am suggesting that the data sources (listed on the maps on the bottom) may be out of copyright… and this map may be out of copyright as well. I’m not sure if German law recognizes “work for hire” principles, but the Berne Convention typically assumes such works (these maps are works for hire) to be 70 years from the date of creation.

It is precisely this kind of mess that I happen to hate this life+70 years stuff, as it can be a pain to even identify who is the "author", much less get a copyright date nailed down to know when the content is in the public domain. Content like this ought to be in the public domain, and to assume a 180 year copyright term (assuming 110 years of somebody's life to make sure they are good and dead + 70 additional years) is borderline insane.

BTW, there is a movement to increase this to life+110 years with the Berne Convention by several content publishers.

All this aside, I am suggesting that these maps may be in the public domain… including in places like Germany. Unfortunately, there is no clear-cut answer that suggest they definitely are. That is the real problem here. Assuming the original map maker died in World War II (a definite possibility based on some of the data sources listed) the life+70 years could have possibly expired already. This is certainly right on the cusp of what would be considered public domain due to age.