Peeking in a recent Io checkin, this was in the IoPlayer/_Readme.txt:
An IoPlayer is basically an executable that when launched: - opens a window with a GL view - looks in it's launch directory for a main.io file and executes it if found or opens an error dialog if not. - glut input comes from the window and gl output goes to the window - a debug window with a stacktrace opens upon errors. The idea is to provide a binary release of Io that can be easily used to distribute software written in Io.
Such a nice packaging method and metaphor. Players, like in virtual machine players.
Update: Madness from Apple