Nature will make its articles back to 1869 free to share online, for certain values of "free" that you might or might not agree with (G+)
Your description of the last link disagrees with the authors of that paper. They specifically say that their paper is not about plagiarism.
Well, it's about setting a baseline for how much copying occurs normally, so that normal copying can be distinguished from plagiarism. Therefore, the question I wrote in the link.