I'm not capable of speaking about OCaml, but I clicked on because I use Lua professionally and where it gets embedded always strikes my interest.
This is using Lua 2.5, current version of Lua is 5.3^, and Lua is not a fast moving language. 2.5 dates from 1997, 22 years ago. So wow, an interesting use of Lua, but as a fairly capable Lua programmer I'm not sure I could code in it.
Instead of using the standard C Lua interpreter (or Luajit), this uses Lua-ML which is an alternate interpreter for Lua 2.5. So moving it forward to Lua 5.1/5.3 would seem to be a lot of work of basically writing a new Lua 5.3 interpreter.
Seems super cool, and a fun project, but...wow. :)