Money is something accepted as settlement of a commitment. Legal tender is a class of money backed by a government in the sense that it cannot be refused as means of settling a financial commitment. However, anything else having the conventional properties of money (i.e. divisibility, fungibility, etc.) can be offered as an alternative mean of settling the commitment and if accepted becomes de facto money. In contrast, an IOU or a bar tab (among other examples) serves only as an acknowledgement that a commitment remains to be settled. Therefore open money is de facto money.