Author: Dr. John Ousterhout Homepage: http://www.tcl.tk/
TCL is Tool Control Language, an open source script language written by Professor John Ousterhout when he was Professor of Computer Science at UC Berkely. It was intended to be a "glue" language that could be embedded in other applications.
Tk is a widget set originally developed to go with TCL, and to provide graphical elements for TCL scripts. Tk has since been incorporated in Python and other languages.
TCL is available in an open source version through Sourceforge, here: http://tcl.sourceforge.net/
It is also available in open source "community" editions, and supported commercial versions from ActiveState, Inc., here: http://www.activestate.com/Products/activetcl/