Personally, I would use an explicit non-commercial license in this case. WTFPL isn't a real license (and isn't considered open-source by OSI). Things like the

Personally, I would use an explicit non-commercial license in this case. WTFPL isn't a real license (and isn't considered open-source by OSI). Things like the AGPL and CC-BY-NC-* are actually written by lawyers and make it clear what you actually want.