You don't have to use it with a replenisher.
A replenisher is a solution that you use to refresh the chemistry. After you use the solution it loses some developing potential, it becomes weaker. In order to regain the full strength of the developer, you pour in a certain amount of replenisher per film developed.
It isn't 100% clear what the replenisher for Acufine actually is, based on the linked to data sheet above. But I'm sure a phone call or letter to the manufacturer would sort that out in a hurry.
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