I have the book and have read some of it years ago. I can't remember if the OS-tasks were an isolated process or just a thread in shared memory.

My first comment would be for a kernel built up using threads in shared memory communicating with signals and mailboxes.

Since 3.0, Minix changed the architecture. Now they are full micro-kernel, use NetBSD userspace tools, have EU funding and some commercial clients.

If you wish I can provide more info.

They are separate processes. In fact it is possible to restart or replace then on a running system.