well, you can buy an index fund tracking ETF such as SPY or QQQ or any of the other ones and the trades would be free as opposed to through a normal brokerage. Using this doesn't equate automatically with day trading.
Right, but it's still a buy and hold strategy. People hear "free trades!" and the assumption is that it's a day trading platform, because $7 to execute a $5000 trade (which is roughly what a normal online brokerage charges) isn't an insane fee if you're pursuing a buy and hold strategy.
It won't be free. There is always execution cost. One form that is mentioned in the article is the 3 days of float they are collecting on all of their client accounts. Now whether the execution costs on robinhood are greater or lesser than other platforms is up in the air. But it won't be free.