Aren't mummers traceable to pre-Christian times? Along with Morris Dancers? And as such, weren't they originally part of a religious rite -- and even if they were originally Christian, isn't their play part of a religious celebration (i.e., Christmas)? Wouldn't that mean that this is part of a state-sponsored suppression of religion?

Does this mean that folks gathering together in their homes to celebrate Christmas with carols and songs and instruments might be violating the law, esp. if the neighbors come over? If I play my trumpet in my home and someone hears me and, for whatever reason, enjoys the music (!), do I need a license?

There's good sense, but there ain't no such thing as "common" sense. If there were, people wouldn't remark on it.