John Ousterhout is the original author of Tcl and Tk.
[http://www.computerworld.com.au/article/301772/a-z_programming_languages_tcl%|%The A-Z of Programming Languages: Tcl]: an interview between John and Kathryn Edwards, Computerworld, 2009-05-08
JO has made several other notable contributions, including Sprite and lfs Tk itself is remarkable.