This article discusses software internally used by Apple.
Acquiring a copy without Apple's consent is illegal and may result in being scammed.
A 4.0 based firmware used for testing iOS devices. Found on an iPhone 4.
After booting up, SwitchBoard.app screen shows up allowing you to choose different options.
They consist of:
The firmware includes standard set of UNIX binaries. apt-get is present, suggesting that there is an internal APT repository.