OSI Affiliate Software is described as 'web-based platform that helps you create and manage an affiliate program for your business'. There are more than 25 alternatives to OSI Affiliate Software, not only websites but also apps for a variety of platforms, including Mac, Windows, Self-Hosted solutions and Wordpress. The best alternative is Avangate. It's not free, so if you're looking for a free alternative, you could try Bytemart.org or Commission Junction. Other great sites and apps similar to OSI Affiliate Software are ShareASale (Paid), Post Affiliate Pro (Paid), Blink (Paid) and ClickBank (Free).
Post Affiliate Pro runs an entire affiliate program from top to bottom, with the exception of processing the financial transactions. However, most payment processors and shopping carts can be fully integrated with Post Affiliate Pro.
With the iTunes affiliate program you can link to media on the iTunes Store, the iOS App Store, the Mac App Store and the iBook Store and earn commissions from purchases made via those links, but creating affiliate links can be time-consuming and fiddly.