The JSLint license is a derivative of the MIT license. The only modification is to add the phrase "Software should be used for Good, not for Evil."

According to the Free Software Foundation, this phrase makes the license unfree. Also because of this phrase, JSLint was unable to accommodate on Google Code and could not get into the repository of Debian free software. Because of this restriction, according to the author, IBM asked Astor to give them a license to do evil so that buyers could use the program.