If they depend on direct hardware access, there are other operating systems that can do that. And if they can do multi-tasking, they can switch to pretty much a

If they depend on direct hardware access, there are other operating systems that can do that. And if they can do multi-tasking, they can switch to pretty much any other operating system. But in this case I bet it's a combination of them not actually having any option other than to comply with the requirements of some old piece of software that is outside of their control. If they were to demand that all software used in those systems were delivered with sources and compilers, they could at least maintain it and port to newer operating systems and hardware. But they don't.