How is this functionally different from a loan? It appears to be identical.
Shopify is betting that they can predict when you'll pay it back, then set a discount that makes them more money than time-based interest. If they lose, they still get their money back eventually, and if they win, hey, that means you grew faster than expected, which is great for everybody.
However, I worked with a woman who was Jewish. She showed up in a new car one day and we went for a ride.
I asked her how and when she went and got the car.
She said "oh I got a loan from the Jewish community" or something to that effect.
I inquired what that meant; she said that she was able to get a loan from some Jewish social circle and she didn't have to pay interest because she needed someone else from the Jewish circle who was willing to back her and pay the loan of she failed to pay.
I didn't ask what the consequences were if she failed to pay - but she just mentioned that "if you know Jewish people... Getting money isn't hard"
You're never required to charge interest, but in most situations if you receive a below-market loan (from anyone other than a spouse) over $10,000 the IRS will impute interest.
The claim that no docs are required is also specious, as, again, Shopify already knows your personal information and real-time cash flow.
I would assume that the pricing is customer specific, which would make it more difficult to publicly advertise a price.