I think the main lesson here is that a scripting interface that lets you make major changes to an application, including building UIs, is a great deal more valu

I think the main lesson here is that a scripting interface that lets you make major changes to an application, including building UIs, is a great deal more valuable than one that only lets you plug in to extension points that the application developer has already thought of. This was, of course, a large part of the reason why Firefox was successful in the days when it was successful. I don't think the idea that things are "very different from the way things were when Stallman began" is very relevant to this. After all, Emacs is one of the best examples of an application whose scripting system has this sort of power.