I would totally do it if it's obviously not for profit. My previous employer asked me to investigate and try to fix a Firefox bug over the weekend; they had not

I would totally do it if it's obviously not for profit. My previous employer asked me to investigate and try to fix a Firefox bug over the weekend; they had nothing to do with Mozilla, and I claimed no prior experience with Firefox (and had none). It was a test of how I would approach a huge codebase. Ended up being a great employer - I learned a lot there and, be all reasonable standards, I got rich doing it.