In addition, making money off the software that others develop and sell on the app store doesn't make Apple more of a software company, it makes them a middle man.
IMO a middle man means you are in between 2 other services, taking a cut off the top.
In this instance, apple not only created and curate the app store, but also invented the concept. In this case they are definitely not a middle man, they are a software company selling access to their software to developers.