made some changes to make it work for me

less2stylus.coffee

# Quick hack of regular expressions to convert twitter bootstrap from LESS to Stylus

fs = require 'fs'

less2stylus = (string) ->
    string = string
		.replace(/^(\ *)(.+)\ +\{\ *\n?\ */mg, "$1$2\n$1	") # remove opening brackets
		.replace(/^(\ *)([^\ \n]+)\ +\{\ *\n?\ */mg, "$1$2\n$1	") # remove opening brackets
		.replace(/\ *\{\ *\n*/g, "\n") # remove opening brackets again (some random cases I'm too lazy to think through)
		.replace(/\ *\}\ *\n*/g, "\n") # remove closing brackets
		.replace(/\;\ *?$/gm, "") # remove semicolons
		.replace(/@(\w+):(\ *)\ /g, (_, $1, $2) -> # replace @variable: with $variable =
			"$#{$1}#{$2} = "
		)
		.replace(/\@(\w+)/g, (_, $1) -> (if $1 == "import" then _ else "$#{$1}"))
		.replace(/\.([\w-]+)\(/g, "$1(") # replace mixins from .border-radius(4px) to border-radius(4px)
		.replace(/,\ */g, ", ") # make all commas have 1 space after them
		.replace(/\.less/g, ".styl")
		.replace(/(\ *)(.+)>\ *([\w-]+)\(/g, "$1$2>\n$1	$3(")
		# need to make sure things like -webkit-background-size are left-aligned
		# need to handle expressions
		.replace(/\ *$/g, "") # remove trailing whitespace

	lines	 = string.split("\n")
	indent	= 0

	for line, i in lines
		if line.match(/^[^\/]?\ *[\w-\*]+: /) # property name
			lines[i]	= line.replace(/^\ */, Array(indent + 1).join(" "))
		else if line.match(/^\ +[\w-]+\([^\$\)]/) # mixin
			line
		else if !line.match(/\/{2}/)
			indent		= line.match(/^(\ *)/)[1].length + 2
		if line.match(/e\(\%\(/)
			lines[i]	= "#{Array(indent + 1).join(" ")}// #{line}"

	lines.join("\n")

names = fs.readdirSync("./less")
for name in names
	path = "./less/#{name}"
	if fs.lstatSync(path).isDirectory()
		path = fs.readFileSync path
	else
		return "error"
	stylus = less2stylus path, 'utf-8'
	fs.writeFileSync("./stylus/#{name.replace(/\.less$/, ".styl")}", stylus)