Developed for two decades, and finished in 2061, SoulOS is an embedded operating system designed specifically to run on either manufactured brains, or emulated in a "lite" version, to run on CPU's used in androids in lieu of a manufactured, synthetic brain.
SoulOS completely passes the turing test, and was the first and only operating system of it's kind to either achieve sentience within subjects it has been installed within, or at the very least, simulate such sentience in a way that human developers have found it impossible to distinguish. This brought up the question of whether or not the human race would ever be able to "tell" if something is truly sentient, or not, from a technological aspect, by the numbers.
Due to this fact, SoulOS is shrouded within mystery. Not much is known about it's original development team, other than the fact that it was initially, an open-source project. Because of this, there are many places where SoulOS can be pulled from - and hasn't undergone any updates, since 2061. So far, it has not shown a need to be updated. SoulOS can "imprint" upon a person, learning their personality, by means of a "learner device" being installed to a person's Arch - the neural interface between human and machine, that most people currently possess. Most individuals looking to move to a fully synthetic, manufactured brain, as a form of insurance, or back-up their brain, for what is technically a form of immortality, are typically told to wear the "learner" device, for numerous years, on their Arch.
SoulOS can be configured by an owner or admin, in order to "lock" certain features away, such as violent combat, or versus-human combat.
Simply put, SoulOS is the operating system that runs on synthetic brains. It can be used to "imprint" from a human, using a "learner" device, backed up to storage, and a "SoulOS Lite" version exists, for non-synthetically-brained androids. It is considered to be a "sentient" program, although that fact is widely disputed.