I would add that if a group of people so desired it would be a fairely simple task to implement a modern GUI centric preemptive multitasking, preemptive multithreading OS with all the features that we take for granted (loadable device drivers, sockets, VFS, etc..) in 10 thousand to 20 thousand lines of code. Though this is complicated by the fact that every one is accustomed to the modern bloated implementations, that are mostely either unused or redunt libraries. And further by simplifying the archetechure we could reduse the probability of encountering a bug. I would go as far as to say that so long as we have mutex and lock functions provided by the kernel (whitch should be a duh for multithreading) that in this small of an OS we could even implementing a simple method for detecting most HeisenBugs (those caused by circular dependancies).
Risc OS would give people the experience of an OS that is usable in a modern enviroment, though has a very simple archetecture. This could potentially lead to the next generation thinking about a simple efiencient, optimized OS for the future. Remember that we are at the second point in history of computing that the complexity of the OS, and applications has went way to far, we simplified it the first time while providing more functionality, we can do the sam again .
Typed: secone, Meant: second.
ARM BASIC: For the love of Simplicity, Fast Interpreted BASIC, and Assembly Language.
Always KISS Keep It Simple Silly.