Can a known donor renounce his legal obligations as a parent?

Unknown; there are no donor-related laws in HI.

What if a known donor attempts to enforce his parental rights when the original intent was to be a sperm donor only?

This may be possible given the lack of statute or case law cutting off the rights of a sperm donor.

Does the state allow for second-parent adoption (i.e., for same-sex couples)?

Second-parent adoption is not explicitly prohibited in Hawaii so this may be possible. (Some courts have permitted this.)

Does the state allow for multiple-parent families (when the child has more than two adults in a parenting role)?

Unknown; this issue has not been addressed.

Does the state recognize “de-facto” or “psychological” parentage (of an “acting” parent without a biological connection)?

Unknown; this issue has not been addressed. However, state statute permits, in dissolution of a relationship, action to grant custody or visitation to a non-parent.