MySpace on Tuesday opened its social network to third-party developers, giving them the tools they need to build commercial applications that can run on the site for free.

In return, MySpace is hoping the new applications will keep subscribers on the site longer, which makes MySpace more valuable to advertisers. Rival Facebook launched in May its software tools for developers.

MySpace is offering the Google-developed OpenSocial set of application programming interfaces. The APIs are for building apps in JavaScript and HTML that can be hosted on any social Web site. Other companies implementing the technology include Engage.com, Friendster, Hi5, Hyves, Imeem, LinkedIn, Ning, Oracle, Plaxo, Salesforce.com, and Six Apart.

"No one is going to need to learn any proprietary technology to develop on top of MySpace," Jim Benedetto, senior VP of technology for MySpace, told InformaitonWeek.

In addition, MySpace is offering an API for connecting Flash applications to MySpace. Flash, which is owned by Adobe Systems, is a set of multimedia technologies for adding animation and interactivity to Web pages.

Finally, MySpace is offering "Restful APIs" for server-to-server communications in running applications. Restful often refers to systems that use any simple interface that transmits data over HTTP without an additional messaging layer.

In launching the APIs, MySpace will give developers 30 days to build their applications before the site starts deploying them. The idea is to give all developers an equal chance of being the first to get applications before the site's more than 90 million users.

Once approved by MySpace, applications will be listed on the site's app gallery, where subscribers can click on the service to have it embedded in their profiles. Links on user pages connect to a "canvas page," where a developer can offer users the ability to configure the application, access services or do any other task. This page belongs to the developer, who can use it to offer advertising or monetize the application in some other way, Benedetto said. "We're not taking any of the revenue generated from the canvas page."

At the end of 2007, MySpace accounted for more than three-quarters of the Web traffic to social networks in the United States, according to Web metrics firm Hitwise. Facebook was a distant second with 12.6%.

MySpace visitors on average, however, spent about 30 seconds less time on the site than a year ago. Facebook visitors, on the other hand, spent about 10 minutes longer on average, according to Hitwise.