Ask HN: Would it be a conflict of interest?

I've been working with a non-profit company for the past five years. I now have been given the opportunity to volunteer at an early-stage non-profit that is in a very similar--if not the same--field. This would just be in my spare time and for fun, but I'm not sure about the legal/ethical issues of doing so. I've asked some other people for advice, but I'd like to hear some more. Of course, I don't expect to get legal advice online. Rather, I'd like to know if I should avoid going into this realm, tread it with caution, or not even worry about it.