It's not illegal to ask a question which in answering, the applicant may offer such information.
In all of the examples you give, the "legal" question is askking something directly relevant to whether the applicant is able to perform a job. What someone does with their free time may give you some insight into how well they would do a job, but it's far less directly connected.
* Marital or family status (ask a working mother about this one if you want your blood to boil)
* Age, apart from legality to work
* Sex or, in most places, sexual orientation
* Citizenship, ancestry, race, or national origin, apart from legality to work
* Disabilities of any kind
* Home address
Most questions that would be reasonable in normal conversation are OK in a US interview, so long as they don't pertain directly or indirectly to "race, color, religion, sex, national origin, disability, or age".
You are not strictly limited to questions that directly pertain to a candidate's ability to do the job. In most private business settings, you can legally choose not to hire someone for any number of subjective reasons. Not staying up late to work on open source projects is certainly one of them.
On the other hand, if you have a strong preference for someone who codes in their spare time, and you care about not being a douche, you should mention that preference in your job requirements. It's not cool to waste people's time.
In all of the examples you give, the "legal" question is askking something directly relevant to whether the applicant is able to perform a job. What someone does with their free time may give you some insight into how well they would do a job, but it's far less directly connected.