This may be a silly question, but why does an open source project need revenue? Or employees? Couldn't Mozilla's few core projects run on volunteers?
$500 million in annual revenue and $6 million CEO compensation packages are well in excess of what other similar-scope projects get by on. Mozilla accounts for somewhere between 30-50% of all funding in open-source - if you sum up the Linux foundation, the Wikimedia foundation, the Apache foundation, KDE e.V, the Gnome foundation... it's still less than Mozilla