In the implementations part of the wikipedia page https://en.wikipedia.org/wiki/Active_Scripting#Implementatio... you can see there were a number of available scripting languages for use on IE. For some reason it doesn't mention the ones from ActiveState - the current ActiveState python doesn't seem to be Active Scripting enabled but back when this technology was useful it was - maybe it just provided the python version mentioned on the wikipedia page with some extras though.
on edit: added missing word.
Edit: That said, maybe webassembly is a way forward.
"Vugu: A modern UI library for Go+WebAssembly"
I found this bit to be of particular interest. Why would anyone want to selectively execute code within a comment block? That seems to me to be a Bad Idea™
Obviously modern HTML tags with fallbacks, @supports in CSS, and proper feature detection instead of hardcoding are the better approach nowadays since everyone finally agreed to follow the standards reasonably closely and you don't need version specific hacks rather just checks that something is supported.
You know you have a problem when you need to alter web standards in order to let programmers get around your alterations of web standards.
As a new HTML coder back in the day these conditional comments were really odd to me. Thankfully we don't have to deal with that much anymore although IE 11 is still out there, lurking.