Active option means that a contract has been accepted, however it is in its option period.
( inspections, feasability, etc.....) During this period the buyer may opt out if there is something not acceptable with the property and forfeit the option money before the ernest money becomes at risk.
So the answer is no the seller cannot entertain or accept another offer until the prospective buyer opts out or the deal falls apart. You can however make a back up offer in the event that the property does not close the sellers will be aware of your interest.
Hope this Helps!