
The 501 developer idea is deeper than that. 501 developers do not go home and continue to code, doing things such as contributing to open source projects or write about software development. The implication is that being a 501 developer is a bad thing.
Now I don't consider myself to be a 501 developer. But I wouldn't mind being one. Who wants to stay at work late? Not me. Not unless I am working on my own startup where my work might make me rich. That is not going to happen when you work for the man.
I have met plenty of 501 developers in my career. They have other priorities. Development is just the day job that pays the bills for them. That is not a bad attitude to have. This helps you from being exploited on death march style projects. You also don't waste time at work and lower your effective hourly wage by working extra hours. Those developers may be the smart ones after all.