COINBASE owns GDAX. It’s the same company. It’s very easy to sign up, just use the same info as on COINBASE.
HOW ARE FEES PROCESSED?
A 0.25% taker fee for all BTC books and 0.30% taker fee for all ETH and LTC books is collected on each trade during the day. At the end of the day (UTC 00:00), a rebate is calculated and issued. The amount of the rebate issued is calculated on the percentage of total exchange volume, per product, that a trader has participated in over the past 30 days.
For example, If 100 BTC was traded on Coinbase’s BTC/USD order book in the last thirty days and you accounted for 1.1 bitcoin, you account for more than 1% of the total volume and receive a rebate of 0.01% that day and pay an effective taker fee of 0.24%.
The rebate is issued in the quote currency.