the og scan of book of kells was done by a Swiss publisher in the early 90s. since you can't copyright a scan, and the book itself is in public domain, anyone can then take the scans (if they can get hands on the high dpi originals or whatever, or do a high dpi scan of the reproduction) and publish them as whatever they want. "the complete encyclopedia of human knowledge (only $99.99 if you call now)" "the illuminated authoritative book of kells (comes with your own one of a kind handmade Irish cross)" etc. you can get the scans themselves (afaiu its at matching dpi, if not the same format) from a 2006 trinity college dvd of book of kells.
the op is an announcement of the completed rescan effort, with modern technologies and modern dpis. with a companion iPad app and a website that have consumer grade renditions of those modern research grade scans.
it's a statement of fact, so we can just leave it at that. but the explanation as I understand it and I'm not a lawyer, is that scan or a facsimile is a mechanism of reproduction, and the act of reproduction doesn't give you copyright. work, derivative work, original work, demonstration of originality have all precise definitions, but in laymen terms which is also my understanding, your derivative work has to be creative and original in its own right to have a copyright.
So, if you scan it but add some clever upscaling mechanism, dynamic color curves, hyperspectral data, texture capture detailing the 3D surface, and use all that through some perceptual integration to give you a better reproduction than just a mechanical scan, you might be entitled to not have your case thrown out of court immediately.
Presumably, because it isn’t transformative enough to constitute a derivative work. Otherwise, making a copy of free works would allow one to put those works back under copyright.
Global Grey was popular on HN a few years back, and I bought the whole collection.