$ cat JSCAD.minimal.js 
module.exports=function main(){return require('@jscad/modeling').primitives.sphere({radius: 50})}
$

I have it online on my webserver as well, and can start openjscad.xyz with it easily, and it just works:
https://openjscad.xyz/?uri=https://stamm-wilbrandt.de/en/forum/JSCAD.minimal.js

Then I tried to use "data" protocol:

$ cat doit
#!/bin/bash
browser=firefox
browser=chromium-browser

$browser "openjscad.xyz?uri=data:text/plain;base64,`base64 -w 0 $1`"
$ ./doit JSCAD.minimal.js 
Opening in existing browser session.
$ 

But that URI does not work:
https://openjscad.xyz/?uri=data:text/plain;base64,bW9kdWxlLmV4cG9ydHM9ZnVuY3Rpb24gbWFpbigpe3JldHVybiByZXF1aXJlKCdAanNjYWQvbW9kZWxpbmcnKS5wcmltaXRpdmVzLnNwaGVyZSh7cmFkaXVzOiA1MH0pfQo=

Is there a reason why data scheme does not work for "?uri=data..."?
If not, can it be enabled?

I ask because this method would allow to share simple JSCAD files in the URL without storing them somewhere ...

I tested, and there is an 8KB URI length limitation on openjscad.xyz. But in case data scheme would work, maybe "...?uri=data:application/gzip,base64;..." would work as well, allowing for scripts with gzipped length of up to 6KB ...

Regards,

Hermann.

P.S:
My GraphvizFiddle tool has a similar Share button approach, allowing to share a design via URL, eg:
https://stamm-wilbrandt.de/GraphvizFiddle/?1705330894960#digraph%20G%20%7Brankdir%3DLR%3B%20JS-%3ECAD%7D%0A