Let's compare Lua to Javascript: People have written NES emulators in Javascript, and they are slow even on a modern PC. The TI-Nspire has a much slower processor than a PC, and Lua is even less suited for emulation than Javascript; it not only has the big problem of not having typed variables (any variable in JS or Lua can point to an object of any type, so the runtime has to do a type check on every operation), but also doesn't even seem to have bitwise operators (which are used extensively in emulators and are inefficient to build out of other operators).

yep but I want castlevania and smb3 on my nspire CX!!!!!!!!!!!!!!!1

Not to mention Lua is in constant danger of seeing functions removed in future OS versions (like what happened to sound in OS 3.1.0)