WTFPL can include a warranty clause (see [0] «Why is there no “no warranty” clause?»)
Also, the Google guidelines consider that WTFPL is recognised as open source by OSI, yet there seems to be some opinion from FSF people that it is free software (see [0] «Is the WTFPL a valid license?»).
Also, the Google guidelines consider that WTFPL is recognised as open source by OSI, yet there seems to be some opinion from FSF people that it is free software (see [0] «Is the WTFPL a valid license?»).
[0]: http://www.wtfpl.net/faq/