I fail to understand what's the point in keeping closed source an operating system that runs only on a platform that ceased to be manufactured 30 years ago, besides maybe the usual patent nightmare, but anyway... if you want to get an idea of how the Amiga worked, the AROS operating system is an Open Source recreation of the old AmigaOS that runs on different architectures, including x86 and ARM, so you can run it on a PC or a *Pi board, either native or hosted as a process.