That was a long blog which essentially would have been pretty common knowledge for most Joy Division fans and/or people interested in astrophysics. And because of that I think the author missed out on raising a bigger and more interesting discussion: (I'll quote one of the comments on his site as that phrases is things rather well)

Interesting, but the article misses the point in all kinds of ways. It was common knowledge (at least, to those familiar with Joy Division and Saville's work) that the image itself was appropriated from an original that was in the public domain. The interesting point here is not copyright, but the way in which an image can come to represent a concept such that it gains new meaning. When the intended audience sees this, they think, "Joy Division", not "pulsar". Hence, when you copy the image by way of Saville, you are appropriating the association that he has established. So, this isn't about stealing images, it's about riding on the coat-tails of a talented designer who managed to create a strong brand.

A proper understanding of what's going on here makes this sentiment: "If you ever want to use the image for your own personal benefit, just make sure it’s clear you have no connection with Joy Division, Peter Saville, etc…" pretty shiesty.