What's also interesting about that old ANN link is that they describe ExecSG as sitting on top of a HAL (not including UBoot).

I'm pretty sure that this didn't eventually happen, and ExecSG had to be adapted for every new piece of hardware. Which means the code, assuming the Friedens even sold it, will have an interesting list of all the hardware projects OS4 was ported to or intended to be ported to. More egg on face for Hyperion if so.