There's a difference between the Mozilla Corporation and the Mozilla Foundation. The latter owns the former. Revenue for the former is not revenue for the latter, though dividend payments from the former to the latter are revenues for the latter.
The Form 990 is for the Foundation. You probably want to look at https://static.mozilla.com/moco/en-US/pdf/Mozilla_Audited_Fi... instead, since that includes the subsidiary Mozilla Corporation. Page number 4 (sixth page of the PDF), the "Revenues and other support" table.
Technically, a not-for-profit taxable subsidiary. (That makes a difference because the company purpose of Mozilla Corporation is still not to make money/raise shareholder value, despite the fact this it is fully taxable like any other company).
Isn't the purpose of Mozilla Corporation exactly to make money which inures to the benefit of its sole shareholder (Mozilla Foundation), making it just like any for-profit company except that it happens to be owned by a nonprofit?
The Form 990 is for the Foundation. You probably want to look at https://static.mozilla.com/moco/en-US/pdf/Mozilla_Audited_Fi... instead, since that includes the subsidiary Mozilla Corporation. Page number 4 (sixth page of the PDF), the "Revenues and other support" table.