I got our writer Robin Laws to write in this format. Elise or I then cleaned it up a little to be compilable. Shawn Steele wrote the interpreter that processes this language when you play a scene.
This language is pretty specialized to King of Dragon Pass’s interaction format. If I were creating a similar game from scratch today, I’d investigate using Lua instead (though the fact that OSL doesn’t require quoting strings was probably a big plus).