Yeah, it looks like I have to specify both the history and readline paths, to make sure I get the GNU libs across the board.
Lua versions 5.1 to 5.3 inclusive are supported, as is LuaJIT.
I have versions of luarocks built for 5.1, 5.2, and 5.3 using versioned directory structures. Looks like on top of the configurations issue when building luaprompt, my install of luarocks-for-5.1 was a bit broken. I re-downloaded the package and built it from scratch, and using the directory flags I was able to install and test luaprompt in 5.1, 5.2, 5.3, and jit.
Might be worth adding a note in the relevant section of the readme that both those flags may be required on OS X.
Thanks for your help. My REPL is finally sane across all versions of lua!