Lisp Operating System (2015)
Summary:<p>- We don't need separate processes if the language we use is inherently safe (e.g., modern Common Lisp).<p>- Without process isolation, it is possible to share large, complicated and possibly mutable data structures (graphs, arrays, user-defined objects) system-wide.<p>- Once it is possible to cheaply share and communicate arbitrary data structures, it is pointless to maintain designated 'file system'.<p>- Not having a file system raises the question of what data should be persistent and what shouldn't.  But on a modern computer, it is feasible to just treat all data as persistent (maybe excluding the youngest GC generation).<p>The best news is that the author is actually working hard to implement this operating system.  The first part - the Lisp implementation - is already in a pretty good shape and could be finished within the next two years:
<a href="https://github.com/robert-strandh/SICL" rel="nofollow">https://github.com/robert-strandh/SICL</a>