I think that making reproductions of work is ok, as long as it is know by everyone involved including the viewer. I have created a lot of reproductions of ceramic pieces for clients who just wanted a little piece of something they saw in a museum for themselves. I do believe that everything is just a copy of something else, so even the art works we cherish as "original masterpieces" are probably just copies of something older.
The piece on the last supper was really interesting. I think the artist was able to bring a contemporary audience to a work of art which is relished for its antiquity. This art work was able to allow the viewer to see the painting in a way it had never been seen before. This is what art is all about, right? Yay!