[fizfaz]

the linked source-archive (at the bottom of the page) compiles without problems on a modern OS, or do you mean an application using it?

[mkumm]

Looking for any software projects that have successfully adopted this approach for extensibility.

[sitkack]

Anything embedding Lua, TCL or Rexx should be nearly identical in structure.

https://en.wikipedia.org/wiki/Rexx