Once downloaded, the file can be emailed out to anyone who requires a copy.  We accept that there is a certain amount of trust implicit in this whole transaction, but that is just an inherent feature of this type of product.  We don’t expect a choir of 100 to laboriously check and reconcile that no more than 100 copies have been made or used.  It is more important that a choir purchases a licence appropriate to their size and manner of use and then they enjoy it!