Mac App Store - Cydia is somewhat of jailbreak equivalent of the App Store for iOS devices. It enables users to find and install open source packages as well as buy special modifications made for jailbroken phones—often with features not approved by Apple. Cydia creator Jay "saurik" Freeman has now announced that he is also building a version of Cydia for Mac OS X, called, appropriately enough, Mac Cydia.
Cydia is generally installed either automatically or as a recommended first step after jailbreaking an iOS device. It was originally one of the first sources of installable packages for jailbreakers, including apps and command line tools, but later offered developers an way to sell software that would otherwise be impossible to distribute via Apple's official App Store. Freeman told Ars in 2008 that he named Cydia after the Latin name for a moth larva that thought of as "stereotypical apple worm."
While it is common to think of Cydia as a jailbreak alternative to the App Store, Freeman says that it exists primarily to distribute modifications for iOS and third-party apps. "There are maybe four actual apps available via Cydia," he said.
Mac App Store
The modifications are based on a framework called MobileSubstrate, which makes it relatively easy to install and update such modifications. For instance, Winterboard—its name a clever twist on the iOS launcher called "Springboard"—allows users to change wallpapers, icons, and other system graphics. SBSettings allows users to swipe the status bar to pull up an Android-esque drop-down panel, which can quickly turn on or off certain settings like WiFi or Bluetooth. And unlocking a phone from a specific carrier requires modifying a background daemon called Commcenter.
Freeman created a new version of MobileSubstrate which has calls simply "CydiaSubstrate." This new version can run on both iOS as well as Mac OS X on the desktop. "Just like you can make all these modifications on the iPhone, you can make these same modifications on the desktop," Freeman said. "Until now, there has never been a way to easily install modifications to the system or third-party applications, as well as keep them updated."
Mac App Store
Such hacks are technically possible via command line tools, hex editing, or other techniques. But such hacks can be difficult to maintain, and generally require some programming knowledge to keep from breaking.
Developers who want to offer users some way to change how Mac OS X behaves—such as adding menu bars on more than one monitor, for instance—could use CydiaSubstrate to build the mod and distribute the resulting software via Mac Cydia.
Mac App Store