The tension between the two urges--one, to push works into the public domain more quickly, and, two, to make sure that works aren't too faithfully copied (even if they would, under scheme one, be in the public domain)--is interesting to me, in part because I feel the same discomfort that I suspect you feel. Something about it feels wrong (maybe from the old moral-rights lizard brain), even though this kind of copying is one logical end result of my deep desire to see the public domain radically expanded.
It's tough to articulate a principled distinction here. Brown seems to have done all an IP-rights-limiter could want: I understand he asks for permission and I understand he gives attribution to the original artist.
He's certainly got me thinking hard about my reaction to the work, which I guess is one way of marking it as art, right?