In a case of a call option with strike $K=0$, then payoff at expiration time $T$ is equal to:
In reality the price of the option on the date of maturity is never equal to the stock price itself regardless of the strike price.
More details following comments:
Having the price of the call option equal to the stock price itself provided that the strike is zero implies that holding the call is equivalent to, i.e. generates the same value as, holding the stock.
However, holding the stock has something that holding the call does not offer, e.g. the right to vote and claim on a share of firm’s property.
Hence, holding the call option is not equivalent to holding the stock. Therefore, the price of the call will always be at least a little lower than the stock price itself.