Most Germans think so. But it isn't. Not in the sense that it's forbidden to have or sell it.
Point is, that the copyright-owner (the state of Bavaria) is not willing to bring it into the book-shops.
However, on Jan, 1st 2016 the whole situation will change, since it'll be the year after Hitler has been dead for 70 years, which means - like with any other author - his texts will be free for everybody (the German word for it is "gemeinfrei" = public-free).
I'm sure, we'll see more than one edition of it in Germany next year.