Having a system that produces the same visual output in 100 years is nice, but to achieve that it is sufficient to maintain the old TeX installation in usable form. We have release versions for this. Why does he think his software should be approaching some state of immutability is incomprehensible to me. Evolution of civilization will bring new requirements, perhaps better way to deal with colors, better vector image notation, better font handling, better web&#x2F;HTML integration, ...