Complex sentence: From any OPAC terminal readers will know instantaneously whether the item they need is available on the shelf or on loan, or being reserved, and if it is on loan, readers will also know the date the item is due for return.
Split into simpler sentences: From any OPAC terminal, readers will know instantaneously whether the item they need is available on the shelf, on loan or being reserved. If it is on loan, readers will also know the date the item is due for return.