... because it is extremely unlikely to work. If you actually want your users to be legally able to use your software without a commercial licence, use a recognised open licence like the MIT licence. Public domain dedications are on extremely shaky ground and give your users no protection.
http://linuxmafia.com/faq/Licensing_and_Law/public-domain.html -- Steven -- https://mail.python.org/mailman/listinfo/python-list
