The messaging on the customer-facing portal describes subscriptions as "fun to discover" and leverages the company's reputation ("relax, we are always here for you") and ease-of-use as key selling points. As for Prime-exclusive deals, right now you can pick up a free month of Dropbox Plus and two weeks of Amazon Rapids for free, among others.

The requirements seem pretty lax too. As a developer, all you need to get in on the program is to offer an app, website or software; have a US business address and sell a subscription that has recurring fees. Amazon takes the internet-standard 30 percent cut of a subscription's first year, and that decreases to 15 percent if someone renews.

"You have full control over pricing, with the option to create different tiers of service, offer a free trial or set an introductory price," according to the Subscribe with Amazon page. "Subscribe with Amazon is a self-service solution that allows you to make your digital subscription purchasable to millions of highly qualified shoppers who trust Amazon to be their primary shopping destination."

That last line is the key here: Amazon is angling to be everyone's goto stop for online shopping, and it's going to use the subscription service to further push that.