Calling it a "paid app promotion app" isn't factually correct. Most of the app developers who participated in AppGratis deals didn't have to pay anything. AppGratis' major revenue source was through commissions from the Affiliate program.[1]
The only justification for the removal of this app is that it was against Apple's AppStore Guidelines & policies.
The only justification for the removal of this app is that it was against Apple's AppStore Guidelines & policies.
[1] http://www.apple.com/itunes/affiliates/