"Linux operating systems - and open source-based software in general - have reached critical marketplace mass," said the study's authors, Bruce Guptill and Bill McNee of Saugatuck Research.

They predicted that the number of companies in "early or full deployment" of mission-critical applications on Linux would grow by 40 percent from 2007-2009, and would then accelerate to grow by 80 percent from 2009-2011.