Twin - a Textmode WINdow environment, by Massimiliano Ghilardi

Twin is a windowing environment with mouse support, window manager,
terminal emulator and networked clients, all inside a text display.

It supports a variety of displays:
* plain text terminals (any termcap/ncurses compatible terminal,
  Linux console, twin's own terminal emulator);
* X11, where it can be used as a multi-window xterm;
* itself (you can display a twin on another twin);
* twdisplay, a general network-transparent display client, used
  to attach/detach more displays on-the-fly.
