Imagine a tiny economy with two people. There is one guy that produces everything humans need and he can produce one day worth of supplies in four hours. But to keep his business running he depends on a piece of software that the other guy wrote, without it he could not produce anything. The other guy happily licenses his software for one day of supplies per day. Now the only thing he has to do besides enjoying all his supplies is to now and then spend an hour of work to maintain the software.