Programs distributed with source code are analogous to the traditional seeds that contribute to a healthy and diverse world food supply. Programs that are operationally disclosed (with source code, etc.) will be adapted to local requirements, through modification and sometimes cross-breeding with other program source code. Each disclosed program contributes to the knowledge base of individual users. Not necessarily all users will modify the software, but even a small fraction of the users doing this can and often will improve or contribute to the knowledge base.
While there may be an API (applications program interface) provided for software development, and this may satisfy 99% of the users, it is the very 1% of users it doesn't satisfy, who are the ones ``thinking outside the box'' and therefore perhaps most apt to advance the state-of-the-art. By shutting off access to that very small percentage of the user-population, software barons have contributed to a situation of intellectual stagnation outside their regimes. In this way they have set the stage for shutting out a certain amount of intellectual diversity.