I am fairly sure the 2 companies currently offering reprinted manuals (Centerline and IAP) do so with permission from ARDONA and pay royalties to them. You would have to call them to see what their policy on this is. The royalties they pay are why the manuals cost more than the cost of a copy.
FYI, the Milano manual by itself is fairly useless in many situations. It assumes you are working in a shop environment that has a full library of manuals and simply says "See GTV-6 Manual" for entire chapters (clutch, gearbox, differential - to name a few). The Centerline reprint includes the missing chapters from the GTV-6 manual.
Copying a manual for personal use is probably "no big deal". Selling and/or distributing to others is definitely not legal without permission from copyright holder. And, ARDONA has been known to pursue legal action over seemingly small things, like logo usage.