Legally or morally? I would say so morally. Legally is anyone's guess but you'd be crazy to take the advice of anyone other than a lawyer on that question.
Because their work was temporary and they don't have any skin in the game, I feel like equity is a bit much. I was thinking some other type of remuneration instead
I'm not really saying the old OSes were better. In many ways we have come a long long way. Yes the command lines in the old OSes were better. They were easier to learn and understand. They had features that seem to be missing in many shells today. Things like autocomplete for example. But mainly I think we need more new stuff. Stuff I don't know is missing. I don't want a return to the old but a look to what would be new.
If you have to use a UNIX shell again, say bash, try looking into the bash_completions package (http://bash-completion.alioth.debian.org/). I hear tell that KSH and ZSH also do dynamic completions pretty well. Not sure if that's exactly what you mean, but I've found tab-completion to be getting better and better.
As for the great unknown, that sounds like basic research. Would love to see more of that stuff, but not many people seem to be paying for it. Still, much research is happening at universities around the world. If I hadn't given up on my postgraduate degree, that might be where I would be today :)
