Aha. There is an interface on Windows but it is the separate “GTK” application. Here is a direct link to the interface version for Windows:
http://prdownloads.sourceforge.net/mp3splt/mp3splt-gtk_0.7.3_i386.exe
In view of the poorly presented site I suggest we give the direct link for Windows (as above). For Mac, it barely seems worth recommending except to advanced users as the site uses Fink or MacPorts distribution even for the GTK version.
I have updated the Wiki page.
Gale