Google has retired Google Gears in favor of HTML5. They’ll however continue to support Gears enabled web applications for Firefox and Internet Explorer for some more (unspecified) time:
In January we shipped a new version of Google Chrome that natively supports a Database API similar to the Gears database API, workers (both local and shared, equivalent to workers and cross-origin wokers in Gears), and also new APIs like Local Storage and Web Sockets. Other facets of Gears, such as the LocalServer API and Geolocation, are also represented by similar APIs in new standards and will be included in Google Chrome shortly.
We realize there is not yet a simple, comprehensive way to take your Gears-enabled application and move it (and your entire userbase) over to a standards-based approach. We will not be investing resources in active development of new features. link.