Check out this post by Asa to get the facts on this:
http://weblogs.mozillazine.org/asa/archives/007658.html

I don't know what's the story. I'm still waiting on a response from Gervase. It seems like Google did pay them to be the default, but localized versions can use localized versions of Google, but no other engine (even when others are more relevant or popular). Also, there appears to be some anger at the suggestion that the Mozilla Foundation is nearly broke.