Conceptually, throwing a bunch of ICs, glue-logic, and some RAM etc. on a PCB is dead easy. The stumbling block here is the PC compatible BIOS. Is there an open source BIOS available that supports all the standard PC BIOS calls ?
You probably could build an ISA bus IBM compatible PC out of microcontrollers, and port one of the open source BIOSes to it, but the utility of such a thing is questionable.
Anything that gets people building more homebrew computers is a good thing in my book.
I am to focus on this in a couple different ways, largely based on either a pub/sub style format for smaller periodic messages, or on a mailbox style format for larger messages (display frames, etc).
I'm still pretty early in the brainstorming process, and this is intended as a hobby/teaching project, but I'd love to have things be useful for everyone using it, and having compatibility APIs are a big way of achieving that.