All we know is that he donated $1000 to reaffirm, in law, that marriage can only be between a man and a woman.
Perhaps he believes that the state should remove all recognition of marriage and just recognize civil unions going forward for everyone with the benefits from marriage.
We don't know, because he hasn't talked about his beliefs. And honestly, I don't believe they're that important when Mozilla has reaffirmed their strive for equality.