It's linked from their offical page: http://www.charliehebdo.fr/

Very much the real deal-- costs $3. It also creates an entry in Newstand.

If you can't read French, you buy the English edition and tap the text to see a translation: http://i.imgur.com/ETunCZv.jpg

From what I understand, this magazine had a circulation of maybe 50,000 but with the most recent edition 3million didn't come close to meeting demand. This is a very creative solution.