Very good point. Depends on the company.

I was fortunate, in that I didn't have a "shower clause" in my employment contract, so I was able to do a lot of extracurricular work.

In fact, it was a principal reason that I stayed at that company. They paid me...OK...for doing the work I hated (managing -but I was also a good manager), and let me have enough bandwidth to do my extracurricular work; which was my true passion.

Basically, the work I didn't get paid for, was what I really wanted to do. They were extremely happy with the work I did for them, which did not reflect my true, personal passion. I feel like I was "just going through the motions," as a manager.

But I also firmly believe that if I am given responsibility for a task, then I do it to the very best of my ability; whether or not I am passionate about it, and I'm actually a really decent manager (for the type of team I led).

After leaving that company, and learning (the hard way) that no one wants to work with a 55-year-old engineer, willing to work at half the wages of far less-qualified people (because I already had my retirement set), I was forced into early retirement, and actually achieved my dream, which is writing code to help out NPOs, for free.

I never heard of that. I'm originally from the EU and in the country I'm from, employers cannot control what you do in your spare time, and do not automatically own what you do outside your day job. In the US that's much more complicated.