The way that you do it matters. Participating as equals in the marketplace you've created is fine. Leveraging data or other things your competitors don't have a

The way that you do it matters. Participating as equals in the marketplace you've created is fine. Leveraging data or other things your competitors don't have access to, is abuse as no one would be able to compete against you in that case. Amazon using data from its own marketplace to know what "Amazon Basics" to produce is one example, Apple being able to use private APIs other applications in the App Store cannot use is another.