How to add a legend to a Kiviat diagram with mutltiple lines? (tkz-kiviat)

Question

I am trying to make Kiviat diagram with multiple lines similar to the example provided here: https://tex.stackexchange.com/a/10503/7892

This is the example code:

\documentclass[]{scrartcl}
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc}
\usepackage[upright]{fourier} 
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{tkz-kiviat,numprint,fullpage} 
\usetikzlibrary{arrows}
\thispagestyle{empty}
\begin{document} 
\begin{tikzpicture}
\tkzKiviatDiagram[scale=1.25,label distance=.5cm,
        radial  = 5,
        gap     = 1,

        lattice = 5]{McCabe,LOC,Live Variables,Halstead N,Variablenspanne}
\tkzKiviatLinethick,color=blue,mark=none,
               fill=blue!20,opacity=.5
\tkzKiviatLinethick,color=darkgray,
               fill=green!20,opacity=.5 
\tkzKiviatLineultra thick,mark=ball,
                 mark size=4pt,color =Maroon

\tkzKiviatGradprefix=,unity=100,suffix=\ \texteuro

\end{tikzpicture}
\end{document}

How can I add a legend to specify the meaning of each line+marker+filling combination?

I have found this, which almost seems like what I want, except that I don't know how to show lines+markers instead of nodes in the created legend: TikZ picture: how to add a legend?

Arrows with labels pointing to the lines might be another option, but seems more complicated and I am also not quite sure how to do it.