BASIC was commonly understood in the 80s despite lots of very different dialects and also in the 90s mostly because of Visual Basic. Is it still true that developers are familiar with BASIC? I would expect that JavaScript and maybe Python replaced BASIC as lingua franca. JavaScript looks simpler because it basically (pun intended) doesn't have a standard library to learn, with all the problems deriving from that.

Java doesn't seem a bad choice because if one sticks to the basics probably everybody can figure out what a simple program does. Smalltalk, I wonder how many people here ever read a Smalltalk source file [1]. Lisp, maybe more, at least to look once at all those funny parentheses (disclaimer, I wrote my fair share of Lisp but I know the effect it does on most people.)

[1] One random Smalltalk project from the list of trending Smalltalk repositories on GitHub https://github.com/svenvc/zinc