I imagine 99% of its use are people maintaining quickbasic legacy apps.

Good question, I'm not even sure what I was looking up when I found that thread, I think I was curious about something else entirely, but as someone who learned to code with VB6 the link intrigued me, I mean come on, that thread title is just great.

I wanted FreeBASIC to have a RAD IDE back when I was still clinging to VB6 as it was being replaced by VB.NET. I hope someday Microsoft open sources bits and pieces of VB6.

Have you checked out Gambas[1]?

1. https://gambaswiki.org/website/en/main.html

We're up to GWBasic, so I'd hope for QuickBasic in its various forms, next.

After that are the various visual basics.

For DOS we are up to 4, hopefully 5 is next which has interesting TUI apps like DOSSHELL as well as QBasic and EDIT and QuickHelp.