> This phrase does not have a single, simple definition that is clear and robust.
Since this is in the scope of, say, a program's source code, the implicit meaning would be "do what you want [with this code]". Explicitly stating that would help, but it's not really that necessary unless you feel like being needlessly pedantic.
Virtually all license agreements are also implicitly bound by jurisdictional laws, so "yet it is okay if i stab you with a knife" would not be a valid interpretation of "do whatever you want" - in a legal sense - unless the agreement is taking place in a jurisdiction in which stabbing someone with a knife is legal.
The implicit meaning is going to be argued over repeatedly.
Particularly when an author says "well, what i really meant by do whatever you want is 'x'"
Depending on how reasonable x is, a judge may or may not buy it.
Note also that the suggested license header is:
"/* This program is free software. It comes without any warranty, to
* the extent permitted by applicable law. You can redistribute it
* and/or modify it under the terms of the Do What The Fuck You Want
* To Public License, Version 2, as published by Sam Hocevar. See
* http://sam.zoy.org/wtfpl/COPYING for more details. */"
This is also bad if it really lets you do whatever you want -
The clause "use it or modify it under the terms of ..." implies there are limitations on how you may use/modify it - in particular, only under the terms of the WTFPL. If the WTFPL truly has no restrictions, this wording is meaningless. Under various canons of interpretation, a judge will usually find that people didn't mean for words to be meaningless.
What limitations/meaning will be ascribed is also up in the air.
Realistically, the right wording to use there would have been "you may use it without restriction, as the WTFPL version 2.0 explains" (or something similar).
Again, you can argue this both ways. But it is just not the certainty it seems some want to ascribe to it.
Since this is in the scope of, say, a program's source code, the implicit meaning would be "do what you want [with this code]". Explicitly stating that would help, but it's not really that necessary unless you feel like being needlessly pedantic.
Virtually all license agreements are also implicitly bound by jurisdictional laws, so "yet it is okay if i stab you with a knife" would not be a valid interpretation of "do whatever you want" - in a legal sense - unless the agreement is taking place in a jurisdiction in which stabbing someone with a knife is legal.