text said: Warning:Outright ban on duplicate and online-distribution of this book. Do not uploaded onto any web servers a part or all of this book;without notice.
well, thats what most of the artists wish, so people would actually buy their stuff rather than download for free. I bet most of the h-mangas you can find have something similar (in japanese at least) on the last page or something.
And you can find many pages from the Namaka doujin here on Danbooru. Besides, if you ask politely, someone will probably magically produce a version without the text - problem solved ;)