Salesforce reseller programme / Partner programme - Apto app - how does work?

This is a type of OEM application where SF allow user to build app and sell it as per there customization.

The AppExchange OEM Edition nevertheless offers developers a proven and secure platform, which allows them to focus on their product innovation without having to worry about the infrastructure. It allows developers to leverage the SalesForce platform to develop and sell on-demand applications, distinct from the run-of-the-mill CRM apps. They have the freedom to fix their own delivery channels, but cannot use the AppExchange Checkout

You can check it more detail here

Salesforce allows you to build an application, called an OEM application, where your subscribers do not pay salesforce.com directly for licenses, but instead pay the OEM partner directly. In turn, the OEM partner pays a percentage of its license revenue to salesforce.com. Typically, salesforce.com loses a few bucks per license, but is still gaining revenue through volume licenses, and they don't have to deal with subscription costs, sales, marketing, etc. The standard OEM agreement prohibits Leads, Opportunities, Cases, etc (the "CRM" part of Salesforce), but allows custom objects, API access, and so on. The OEM wins because they no longer have to deal with hardware and platform software or system upgrades and maintenance, and can focus on building their purpose-built application. Here's more information about the OEM license types.