No, once again a developer doesn't have to live on selling his programs, but for instance he can do any job where his ability to develop will have value on labour market and would be included in his salary. This job can be "developer", and in that case all his production helps for the general functioning of the firm, and will be paid for that. Many people do have such a job. A system administrator, for instance, do write some scripts every time, but he doesn't actually sell them.