Every programming job I've ever had, I've been required at certain points to make open source contributions. Granted, that was always "we have an issue with this OSS library/software we use, your task this sprint is to get that fixed".

I won't say never, but it would take an exceedingly large comp plan for me to sign paperwork forbidding me from working on hobby projects. That's pretty orwellian. I'm not allowed to work on hobby projects on company time, but that seems fair, since I also can't spend work hours doing non-programming hobbies either.