This version is compatible with iOS 4.0 to 4.3.5.

AppSync dynamic library for iOS 4 ONLY.

This is the last version of "AppSync for iOS 4.0" that Hackulous released before they shut down.

This package contains an unmodified copy of AppSync for iOS 4.0, and it functions the same just as the original from Hackulous did. It will still work as well as it did before on iOS 4.

AppSync and jailbreaking are NOT for piracy.

AppSync and jailbreaking are for freedom of your iOS device.

AppSync is a tweak that patches installd to allow for the installation of fakesigned IPA packages on an iOS device.

AppSync can be used to downgrade or clone installed apps, to download fakesigned IPAs (often emulators), and also to assist in the development of iOS applications using Xcode 6 or below.

AppSync should not be used to pirate iOS apps. Please support iOS developers and do not pirate!

I explain the problem with AppSync and iOS piracy rather thoroughly in this reddit post. Please give it a read.