It's just about as permissive as you can get and it's more professional that the WTFPL license.
MIT license do not fulfill, as it require copyright notice and permission notice.
WTFPL do not fulfill the requirement, as it require edited software to change name.
Unlicense do fulfill the OPs requirements.
It really deserve to be upvoted above the MIT suggestion.
It's just about as permissive as you can get and it's more professional that the WTFPL license.