Tcl and Tk are distributed under a modified BSD license:
https:www.tcl.tk/software/tcltk/license.html

• © 1987-2020 Tcl Core Team and Contributers.
• © 2011-2020 Kevin Walzer/WordTech Communications LLC.
• © 2014-2020 Marc Culler.
• © 2002-2012 Daniel A. Steffen.
• © 2001-2009 Apple Inc.
• © 2001-2002 Jim Ingham & Ian Reid.
• © 1998-2000 Jim Ingham & Ray Johnson.
• © 1998-2000 Scriptics Inc.
• © 1996-1997 Sun Microsystems Inc.