One of the blockers to launching my side-startup is the financial investment required to form the business and setup a merchant account. Money is tight for me, and I'd like to keep my costs to a minimum until there is some positive cashflow.
If Square offered an API, I could launch and start accepting money now, holding off on the business formation beyond sole-proprietorship until paying customers have validated my idea. Hell, they can keep the extra $0.15 for that.
So what's stopping Square from doing that? Could they build that out, or are they blocked by, e.g., regulations? (I know nothing about operating a payment gateway)