You don't need a license for data you never see. When I use Firefox to type a comment on HN, that comment goes from me to HN. It doesn't go to Mozilla. Mozilla does not need a license. (And no, Firefox doesn't need a license either, because licenses are granted to people and organizations, not software.)
The only possible reason for Mozilla to need a license to the data I type into Firefox is if Mozilla intends to have Firefox send that data to them.