tk421 writes "Sizing the Linux market ecosystem is no easy task. Downloads of Linux operating systems and applications are not an accurate measure. Analyst firm IDC, however, has a handle on the market and its size, and it's large.
For 2006, Al Gillen, research vice president of system software at IDC, told an early morning audience that the research firm has pegged the Linux ecosystem that includes servers and software to be worth $18 billion. By 2010, Gillen said, the market will be worth $40 billion."