SyntaxHighlighter.brushes.Lua = function()
{
 var keywords = 'break do end else elseif function if local nil not or repeat return and then until while this';
 var funcs = 'math\\.\\w+ string\\.\\w+ os\\.\\w+ debug\\.\\w+ io\\.\\w+ error fopen dofile coroutine\\.\\w+ arg getmetatable ipairs loadfile loadlib loadstring longjmp print rawget rawset seek setmetatable assert tonumber tostring';

 this.regexList = [
  { regex: new RegExp('--\\[\\[[\\s\\S]*\\]\\]--', 'gm'),  css: 'comments' },
  { regex: new RegExp('--[^\\[]{2}.*$', 'gm'),       css: 'comments' }, // one line comments
  { regex: SyntaxHighlighter.regexLib.doubleQuotedString,     css: 'string' },    // strings
  { regex: SyntaxHighlighter.regexLib.singleQuotedString,     css: 'string' },    // strings
  { regex: new RegExp(this.getKeywords(keywords), 'gm'),  css: 'keyword' }, // keyword
  { regex: new RegExp(this.getKeywords(funcs), 'gm'),      css: 'func' },  // functions
  ];
}

SyntaxHighlighter.brushes.Lua.prototype = new SyntaxHighlighter.Highlighter();
SyntaxHighlighter.brushes.Lua.aliases = ['lua'];

<?php
/*
Plugin Name: SyntaxHighlighter Evolved: Lua
Description: Adds support for the Lua language to the SyntaxHighlighter Evolved plugin.
Author: Benny
Version: 1.0.0
*/

// SyntaxHighlighter Evolved doesn't do anything until early in the "init" hook, so best to wait until after that
add_action( 'init', 'syntaxhighlighter_lua_regscript' );

// Tell SyntaxHighlighter Evolved about this new language/brush
add_filter( 'syntaxhighlighter_brushes', 'syntaxhighlighter_lua_addlang' );

// Register the brush file with WordPress
function syntaxhighlighter_lua_regscript() {
    wp_register_script( 'syntaxhighlighter-brush-lua', plugins_url( 'shBrushLua.js', __FILE__ ), array('syntaxhighlighter-core'), '1.1.1' );
}

// Filter SyntaxHighlighter Evolved's language array
function syntaxhighlighter_lua_addlang( $brushes ) {
    $brushes['lua'] = 'lua';
    return $brushes;
}
?>