The provided lovely patch adds it under the module name "json". A modified extract from the project's original readme follows
...
A lightweight JSON library for Lua
json = require "json"
The library provides the following functions:
Returns a string representing value encoded in JSON.
json.encode({ 1, 2, 3, { x = 10 } }) -- Returns '[1,2,3,{"x":10}]'
Returns a value representing the decoded JSON string.
json.decode('[1,2,3,{"x":10}]') -- Returns { 1, 2, 3, { x = 10 } }
null values contained within an array or object are converted to nil and
are therefore lost upon decodingjson.encode() only encodes to a compact
formatThis library is free software; you can redistribute it and/or modify it under the terms of the MIT license. See LICENSE for details.