The income derived from selling out-of-the-money call options combined with the high dividend yield of the stocks in the portfolio less the cost of index puts to help protect portfolio value is adequate to continue the monthly dividend payment. Since the fund is only writing calls options on a limited portion of the portfolio, if call premiums contract, the fund would be able to write on a larger share of the portfolio and maintain the dividend. It's a wonderful safety net!
This ETF is a p.o.s. and I wish I had never bought any of it. Management of the fund should consider liquidating and giving us the money back, since it is worth so much less than the sum of its holdings.