The JSLint license is a derivative of the MIT License. The sole modification is the addition of "The Software shall be used for Good, not Evil."
According to the Free Software Foundation, this clause makes the license nonfree. The clause has also prevented JSLint-related software from being hosted on Google Code and from being included in the Debian free software package repositories. Because of this restriction, according to Crockford, IBM asked Crockford for a license to do evil, such that their customers could use it.