Uh... all this is about is not sharing company secrets. That's a pretty normal request from employers around the world.
I'm not "enslaved by my employer". If my employer feels like firing me based on what I do during my time off, fine - I'll go work for another company. There's no shortage of job openings and there's a huge shortage of talent, so it's their loss. The things that employees get fired for doing during their time off tends to revolve around being a total dick - IE, making fun of homeless people. I'm not saying it's right that they can be fired over that (seems a bit messed up that they can be), but also... come on, really? What made anyone think that was a good idea? The company fires you because they don't want to be associated with someone who is a dick. Their employees are their public face. Even in your time off, you can't make your company look bad. Especially if you're salary... if you're salary, you're getting paid all the time, whether it's during working business hours or not. Hourly employees might be more free to do whatever when they're off the clock, since they're not collecting money during that time.
Back to the original topic of Apple employees not distributing apps, that makes sense to me. It's a free marketplace - Apple doesn't want the appearance of corruption. If Apple employees were allowed to distribute apps on the app store, other people would cry foul and say that those employees were tipping the scales. The non-Apple employees might stop making apps for fear that it's a waste of time and that the field is leveled against them.