There are situations that produce cause for editing to deposits that are open in The Financial Edge. The open status just gives a status for certain types of editing.
You are able to void payments from a deposit that has been posted if it has a status of open. The distribution of a deposit is derived from the payment applied. If a distribution of a posted deposit needs to be changed you have to do it by voiding the payment. This why you have the option to have an open posted deposit.