Well, I don't know if money needs do be dept, but I see two characterisrics of dept money which I think are cruical to any money system.
Whenever you raise a credit you need to deploy economic activity to be able to pay it back. So dept money creates a relation between the amount of circutlating money and economic power.
Second, debt money is destroyed when credit ist payed back. This, at least in theory, keeps the amount of circulating money stable.
Among many things in circles I really like I don't belive that the unlimited creation of money can provide a stable system.