The three files in the src/ subdirectory,
  tidy.h
  utf8.h
  utf8.c
are derived and modified from
HTML Tidy Library Project (http://tidy.sourceforge.net/).

    Copyright (c) 1998-2008 World Wide Web Consortium
    (Massachusetts Institute of Technology, European Research 
    Consortium for Informatics and Mathematics, Keio University).
    All Rights Reserved.


showtext also includes the WenQuanYi Micro Hei font file, with copyrights:

    Digitized data copyright © 2007, Google Corporation.
    
    Copyright © 2008-2009, WenQuanYi Project Board of
    Trustees, All rights reserved.

    Droid Sans Fallback extension interface
    ( http://wenq.org/index.cgi?Fontopia(cn) ),
    copyright © 2008-2009 mozbug and Qianqian Fang

