This article discusses software internally used by Apple.
Acquiring a copy without Apple's consent is illegal and may result in being scammed.
Kernels for Apple's A6X, A6, A5X, A5 and A4 processors, as well as the iPod Touch 3G and iPhone 3GS, are included. Interestingly, there is also a kernel file relating to the iPod nano 7 processor - s5l8740x. This build is known to be able to run on iPhone 4S, iPhone 5, iPod Touch (5th Generation), iPad 2 and possibly other devices.
This firmware has the kernel version
Darwin Kernel Version 13.0.0: Sun May 20 20:05:20 PDT 2012; root:xnu-2107.1.78~6/DEVELOPMENT_ARM_S5L8950X.
Haywire Firmware Findings
In /var/mobile/Library/Assets, you will find a folder containing the name haywire. Inside, you'll find multiple folders seemingly used for restoring. When looking in these folders, you'll find the codenames B137 and B135, with encrypted development components for each, as well as an encrypted ramdisk, with no known keys. They also have iBSS, DeviceTree, and Kernelcaches, but nothing more. Upon further exploration, the heavy lifting is done by a modified version of PurpleRestore built into /System/Library/AccessoryUpdaterBundles/Haywire.bundle. A form of this bundle can also be found in certain production firmwares in the same directory.
After booting up, SwitchBoard.app lets you choose from a slew of apps. They are: