The original authors of the Wikipedia entries will not receive any of this money, but they are acknowledged on the last 30 pages of the book, which lists the handles of all the authors in the most miniscule font possible. However, neither articles nor illustrations are directly attributed to any author. Because the Wikipedia is licensed under the GNU-FDL license, printing this material is not only perfectly legal, but also in the spirit of the Wikipedia project. However, it would have been nice if Bertelsmann gave more credit to the authors.
Of course, the printed version could not include every keyword in the online version of the German Wikipedia, so the publishers restricted themselves to about 50.000 keywords and 1000 illustrations. Overall, the printed version includes about 20.000 articles, which were abbreviated by the editors.
It's important to note that this printed version is not an encyclopedia, but instead a dictionary that is based on the 20.000 most read articles in the German Wikipedia. Most entries are only a few words long. If you wonder about what this book looks like, Google Books already includes a preview of the text and, in keeping with the GPL license, the publisher has made the text available for download.
The real question, however, is why anybody would want to buy a printed and abbreviated version of Wikipedia. After all, you lose all of the advantages of full-text search and the ability to edit articles in this printed text.
It is worth noting, too, that this is not the first time the German Wikipedia has been published. German publisher Zenodot tried to market a Wikipedia-based encyclopedia in 2005, but the project was cut short because there was simply no demand for it.