NetApplications is out with a couple of new metrics of market share for operating systems and browsers, and the news is good for open source. Topping their findings, Microsoft Windows' market share has dropped below 90 percent for the first time in its measurements. The share erosion is largely attributed to increased interest in the Mac platform, but Linux is cited as on the rise as well. In addition, for the first time since it launched its metrics, NetApplications' data shows Firefox's market share topping 20 percent.