You are a technical criminal, if you have sung "Happy Birthday" without permission. To not be universally eligible for lawsuit under Copyright infringement Law, you are signing to give toleration to spontaneous tribute.
Today, you can be lawfully fined having been oblivious to an existing work-- even without the intention of plagiarism. It's as if there's no excuse for not having known a previous work.
We SHOULD have freedom upon NOT claiming credit, WITHIN knowledge or intention of misleading.