I'm not picking on you, I am pointing out the duplicity involved in your actions. You speak of freedom, while denying the people who's work you use the ability to benefit back. Because of how insignificant the work involved in your effort is, it really shouldn't be something that requires the GPL3 to protect it.
They cannot use your code, without giving up all the freedoms they granted you in the first place. I would call your actions two-faced.
GPL3 code cannot go into the public domain code without making the codebase GPL3, so your code is entirely useless to the public domain developers who's code you use. This is not Fudd, this is Fact.