People should stop inventing their own vanity licenses; there are enough popular, legally-sound options available for any reasonable licensing schema.

If you want to ensure everybody who receives your code can modify it, use the GPL or LGPL.

If you want to disclaim your rights to the extent allowed by law, use the BSD 3-clause or X11 (aka MIT) licenses. These are one step above the public domain, and are legal even in jurisdictions which do not recognize the public domain.

Do not use: some license a non-lawyer thought up in a fit of pique after mis-reading somebody else's license. This applies to the author's TPL, the infamous WTFPL, and similar poorly-considered licenses.