In a talk delivered last Wednesday at the Mozilla Summit in Whistler, Canada, Pascal Finette, director of Mozilla Labs, asked an audience of more than 150 Web developers a hypothetical question: what would an "open" Web app store look like? The answer could play an important role in the future of personal computing.

The success of Apple's app store, as both a consumer phenomenon and a new stream of revenue, has changed the software landscape--but only on mobile devices. Now the race is on to adapt this model by developing an app store for the Web itself. In a Web app store, developers could sell applications that would run on any device with a Web browser, independent of hardware or the operating system.

Google announced plans in May to create the Chrome Web Store, which will integrate directly with its Chrome browser. Microsoft also recently began offering Web app versions of its office software.

Also in May, the Mozilla Foundation, a nonprofit organization that provides the Firefox Web browser and other software, revealed its own plans to build a Web app store--one that it promises will be more "open" than anything else. An open strategy-one based on open standards and unrestrictive licensing--has helped the Firefox browser gain market share from Microsoft's Internet Explorer, and the Mozilla Foundation is betting that the same approach will attract users and developers to its Web app store.

Mozilla's vice president, Jay Sullivan, also laid out the principles of an open app store in a blog post last May. The first principle, Sullivan argued, is that an open app store must host only applications based on open standards, including HTML5, CSS, and Javascript. This would preclude apps that use proprietary technologies like Flash and the Unity 3D graphic plug-in. (Although perhaps not everyone agrees with this requirement. Google's announcement of its Chrome Web app store included a demo of the Lego Star Wars game, which includes the Unity plug-in.)

Sullivan also argued that an open Web app store must work equally well across all browsers, should be accessible to all developers, and should not gather user information. Finally, he said, it should have transparent app review guidelines--which would distinguish it from Apple's iPhone and iPad app store.

A few specialized Web app stores already exist. For example, in 2006, Salesforce.com, the enterprise customer relations management platform, launched its own app store, now called the App Exchange.

App Exchange has more than 400 native apps running on Salesforce.com's own platform, as well as more than 1,000 third-party apps that integrate with the Salesforce.com platform. It might not sound like a large library, but according to Chuck Ganapathi, senior vice president for products at Salesforce.com, those apps have been downloaded or test-driven 350,000 times, and all of them are "serious business apps," rather than the entertainment that dominates most app stores.