Supporting the nonsense that moog is doing is not good for the iOS Music Community.
I owned a iPhone since 2007 and a iPad since 2010 and have purchased 100's of apps and the majority of them are music creation apps from The top Rated Developers like Korg to the up and coming Basement Developer that can still code a kick ass useful app. Not one of them had an optional in-app purchase to buy a midi add on. (Well there was one that failed) Midi always came standard or none at all.
There are developers who paved the way for iOS to have a perfect MIDI / CoreMIDI implementation and shared the knowledge through the developer community for FREE so everybody can be on the same page and for music apps to work together in harmony. Which helped make iOS Music Making and incorporating the iPad or iPhone into your existing hardware or software setup what it is today!
In my opinion moog is taking advantage of its loyal customers and cult followers buy 1. Charging for MIDI Out, and 2. Charging a whopping $5 bucks. Even if some picked up the app for a $1 which earned moog all those 5 Star reviews to sell @ $29.99, I feel they still have the right to boycott the MIDI Out fee especially if they know and respect the history of MIDI.
Not even the Legendary Dave Smith sells MIDI as a option on his hardware synths.