I have seen hiring manager on this site say they wouldn't hire anyone without opensource experience. Sometimes they say something wishy-washy about how contrib

I have seen hiring manager on this site say they wouldn't hire anyone without opensource experience. Sometimes they say something wishy-washy about how contributing to open source is such a specialized skill that they don't have the bandwidth to train someone new. At other times they are more willing to blatantly admit that they just want someone who's capable of spending all their free time writing code. I tend to wonder about the legality of it all. Since when did judging candidates on what they do off-the-clock become acceptable? To make it easier, if I don't have time to do open source because I am heavily involved in my religion, does that start to toe the line of acceptable work qualifications.