Licenses written by amateurs are known as crayon licenses. Such are unlikely to be touched by anyone because A: they have not been tested in court and B: are likely to be filled with loopholes, inconsistencies and ambiguities because C: they have not been written by a lawyer and D: they have not been tested in court.
Viewing post in How do I license my game assets?
I’m not sure, I’m afraid. I’ve heard that even licenses can be under copyright, or at least the writing describing them.
If you wish to be 99% confident, your only choices are to either get a lawyer to write a license for you, or copy freely available licenses like those of Creative Commons. None of those are ideal, I know, but please don’t kill the messenger :).