What he's counting on is that the value of BTC vs other currencies will continue going up.
He gave an example of it, and no one saw it for what it is.
You deposit 1 BTC worth currently $100 (more like $142 right now) today. It gets listed internally as a $100 deposit. When you wish to withdraw your BTC, he converts your $100 into BTC at current market prices. Let's say it's now worth $142 per BTC. You get 0.70422535 BTC (because you only have $100 in BTC on account), but he takes a 2.25% fee from that too. You get back 0.68838028 BTC. In no way do you "deposit 1BTC" and get back 1BTC (unless the value of BTC drops)
Of course he can afford to pay 4% interest. He's betting on BTC growing in value. The only way to get more BTC back is if the value of BTC drops. I for one think we are well past that. When BTC hit $100 it became newsworthy and more people are interested now.
Ok. That makes sense.
Why didn't he post this example when I asked him how he plans to make money?
His response made absolutely no sense to me.
What Slackware has said makes sense, but it's nothing to do with what laffenlarry has said. laffenlarry will not be holding deposits in bitcoin; he believes it has no value.