> humans can't either as they haven't produced it. If there is guaranteed no one which can claim ownership it often seen as being in the public domain.

Says who?. The US ruling the article refers to does not cover this.

It is different in other countries. Even if US law says it is public domain (which is probably not the case) you had better not distribute it internationally. For example, UK law explicitly says a human is the author of machine generated content: https://news.ycombinator.com/item?id=47260110