Is it okay to have sex during period?

Yes: This is fine, but it may be messy and uncomfortable for you both, that being said, it is perfectly acceptable.

Yes: It's ok, just don't use it as a birth control method.

Yes: It's ok to have sex during your period, just a little messy. There's no increased risk of infection, if that's what you're worried about.

Yes: There is no danger to you or your partner at all. Some don't like it - but some don't like to eat food that is not well-done to avoid seeing any blood. It's fine and some find it very pleasant since the risks of pregnancy are the lowest at that time. Enjoy what you do.