Except the minor detail that any for-profit is in fact legally OBLIGED to maximize profit for its shareholders.
A "non-profit" status simply gives the organization certain tax advantages because the state understands that the organization is acting on the best interest of the community, rather than its shareholders. But if a for-profit wants to do the same and not take advantage of said tax benefits, that's up to the shareholders to decide.
It's not an implicit nature, it's an explicit legal requirement.
A company can be created for many different purposes.
http://en.wikipedia.org/wiki/Dodge_v._Ford_Motor_Company#Sig...
There are also various protections for minority shareholders in privately held companies to prevent majority shareholders from screwing them over.
And there are various rules about how the company's officers need to pay attention to the shareholders.
In this case, there is precisely one shareholder: the Mozilla Foundation. So the various minority-shareholder protection stuff does not apply, but the officers of the Mozilla Corporation do need to pay attention to what the Foundation wants the Corporation to do. And what the sole shareholder wants the Corporation to do in this case is decidedly not to maximize profit.