Between them, the Mozilla Foundation and Mozilla Corporation – which provide the open source Firefox browser and Thunderbird E-mail client – have turned in revenues of $52,9-million for 2005. 

Mitchell Baker, CEO of Mozilla, has disclosed in his blog that about $29,8-million of those revenues accrued to the Mozilla Foundation.
Most of the revenue, to both entities, came from  search engine relationships, with the remainder a combination of contributions, sales from the Mozilla store, interest income and other sources.
Baker adds that the 2005 figures compare with 2003 and 2004 revenues of $2,4-million and $5,8-million respectively.
Combined expenses for 2005 came in at about $8,2-million.
The Mozilla Foundation was established in 2003 as a non-profit organisation providing a home for the Mozilla community and stewardship for the assets of the project. The Mozilla Corporation was established in August 2005 to guide development of Mozilla products.
Baker explains that most of the revenue comes from the easy "search" capabilities built into Firefox and the related revenue relationships with the search providers.