"That Symbolics would have not gone out of business if Genera would have been free software and portable is speculation." Two different things. I was claiming

"That Symbolics would have not gone out of business if Genera would have been free software and portable is speculation." Two different things. I was claiming that Genera would still be around if it was Free Software - this is by virtue of definition. Symbolics being in and out of business has nothing to do with it. A totally different thing is that I think Symbolics stood a very good chance of surviving if it had made its software more portable. It's a good thing you mention Franz, because they're almost as old as Symbolics, and still around, largely due to the fact that their system is easily portable. They don't waste immense amounts of engineering resources on supporting platforms, but dedicate it to improving features and performance and more importantly responding to customer needs. "1) repeating the design of the past (with the same problems and maybe slight improved. There has been lots of talk and little action. It's difficult because we don't have the hackers with knowledge and time for that." It's difficult to do because when you get down to it, Zetalisp sucked for systems programming. Portable Standard Lisp, Interlisp, CMUCL/Allegro/Clozure (anything with LAP and VOPs) provide a much better model for how to build a Lisp runtime. It's also difficult to do because people like to waste their time imagining how awesome hardware type-checking on FPGAs would be and how the new Lisp OS will have super-duper database-backed storage and network transparency and etc. etc. "2) doing a new design which gets rid of the limitations of past designs (single user, single image, no security, ...). That's even more difficult." The key is the namespace. Symbol identity needs to be preserved across users/processes, symbol values don't. This is actually a much simpler problem than you assume.