Max Klein does not exist. He is an identity created by Mark Essien (www.essien.org).
Mark Essien has two companies registered in the UK one "Qubikle Development LTD" (www.qubikle.com)and a second "Feather & Moor, Ltd" (www.feathermoor.com).
The namesakes of Feather & Moor are Joel Feather and Tracy Moor. BOTH of these individuals don't exist, they are again creations of Mark Essien. The pictures used for Joel are taken from istockphoto (http://www.istockphoto.com/stock-photo-1997908-waiting-for-y...)
whois results for maxkle.in and markessien.com have the same telephone number.
Feather & Moor, Ltd has approaching nearly 300 applications on the appstore. These apps are "cookie cutter" apps that contain pictures and simple text.
The signing identity on the applications names qubikle.
A cursory googling of the text in the screenshots of some of the applications reveals that text is taken from wikipedia and other pages without attribution.
OPINION:
I don't know what the contents of the "other" email was but looking at the apps from "feather & moor ltd" it doesn't strike me that these are wonderful apps of substance targeting niches but instead low quality keyword targeted cookie cutter apps using content without permission.