The following is quoted from the TkZip "About" screen.
This program is copyrighted shareware. This is an unlicensed, freely distributable
copy of TkZip version 1.1.3. Permission to use, copy, and distribute this
software and its documentation for any non-commercial purpose and without
fee is hereby granted, provided that this copyright and permission notice
appear in all copies of the program and its supporting documentation.
Modification for personal use is also permitted.
Non-commercial use is interpreted fairly liberally. If you wish to install your
personal copy on your workstation at work for casual use, this qualifies as
non-commercial. If you are a sysadmin wishing to make it available at your site
as an unsupported tool for casual use, that's fine too. Licensing for personal
or casual use is appreciated, but not required.
If you wish to redistribute it as part of a package for which you charge a fee,
except as noted below, that qualifies as commercial use, and requires a license
from the copyright holder. If you're a sysadmin wishing to make it a formally
supported tool for your users, you need to contact me about licensing. If you
regularly use it in your work, you should license it. Commercial, institutional,
and government users are expected to license it. If you are in doubt, contact me.
Distributors of Linux, FreeBSD, or other free Unix variants, commercial or
otherwise, and regardless of medium, are specifically exempted from the
non-commercial restriction above with respect to inclusion of an unregistered
copy of TkZip with their distributions, so long as the code is not modified
(except as authorized by the author - usually for compatibility with the
distribution's installation procedures) and is sourced from an authorized
repository (like this one), and the author is duly notified of such
distribution. Additionally, distributions sourced from a standard public ftp
site, such as Sunsite or any of its mirrors, incur no obligation to notify the
author.
Robert Woodside and Woodsway Consulting disclaim all express or implied
warranties with regard to this software, including, but not limited to,
warranties of merchantability or fitness for any particular purpose. In no
event shall Robert Woodside or Woodsway Consulting be held liable for any
special, indirect, or consequential damages, or any damages whatsoever
resulting from loss of use, data, or profits, whether in an action of contract,
negligence, or other tortious action, arising from or in connection with the
use or performance of this software.