When I first saw "Categories of Free and Non-Free Software" on gnu.org,
I was puzzled as to how a software package could be Free but not Open,
or Open and not Free. This lead me to write "A spectrum of Software and
Usage", a still unfinished article. Now I find HUNG Chao-Kuei, who drew
the categories of ... software image has does used the spectrum very
effectively in his blog.
Which Color of the Color TV is More Important?
http://blog.ofset.org/ckhung/index.php?post/2007/08/14/Which-Color-of-the-Color-TV-is-More-Important
