Writing an OS isn't that hard. After all, Lion's Commentary on Unix is only 250 pages. But if you actually want the OS to be useful and have modern features, t

Writing an OS isn't that hard. After all, Lion's Commentary on Unix is only 250 pages. But if you actually want the OS to be useful and have modern features, then you're looking at hundreds or thousands of person years rather than a couple months. Plus all the time you'd need after convincing the world to port their software to your new OS.