MOUNTAIN VIEW, Calif. – Sun Microsystems and Google announced a multiyear partnership Tuesday to help spread and develop each other’s software, a deal that includes OpenOffice.org, Java and OpenSolaris from Sun, and Google’s Toolbar ? a direct challenge to Microsoft?s Internet dominance.

The partnership begins with a modest step: Within 30 days, the Google toolbar will become a standard part of the software people get when they download Java from Sun’s Web site. The Java Runtime Environment is downloaded 20 million times per month, Sun Chief Executive Scott McNealy told CNET.Com.

“What Netscape did for the Java Runtime Environment, we believe the JRE can do for the Google toolbar,” McNealy said at a news conference here, referring to the 1995 deal Sun made with Netscape, then the dominant maker of Web browser software, that helped legitimize and popularize Sun’s Java software technology.

Sun also will benefit from the toolbar bundling. “There is direct monetary value for us from being a distribution mechanism for the toolbar,” said John Loiacono, Sun’s executive vice president of software. And Google will significantly increase its purchasing of Sun servers, though neither company would say which models.

The partnership matches two companies with a shared vision of a world being remade by ubiquitous computer networks. Where Sun wants to provide the back-end infrastructure such as servers at Google, eBay and SalesForce.com, Google wants to be part of the daily lives of everyday computer users.

The software the companies are working on all directly compete with Microsoft–for example, Java provides an alternative programming foundation to Windows and Microsoft’s .Net, and OpenOffice competes directly with Microsoft Office. The Google Toolbar, meanwhile, leads to Google’s services and not those Microsoft is trying to promote through MSN.

Google CEO Eric Schmidt sidestepped any direct mention of competition with Microsoft. But in an interview, Sun President Jonathan Schwartz was less reserved. “Do you see Google joining forces with Microsoft on the evolution of .Net? Last I checked, no,” Schwartz said.

Many elements of the partnership remain secret, but Sun executives offered some hints and details.

The companies will conduct joint research and development and joint marketing, Loiacono said, and Google will increase its involvement in the Java Community Process and other technologies.

McNealy said Google will become involved in Sun’s open-source OpenSolaris. “There’s a huge alignment strategy with research and development, (involving) OpenDocument format, OpenOffice and OpenSolaris.?

One question is how the partnership will help advance Sun’s vision that “the network is the computer.” Google has a powerful data center packed with computers and a personal connection to millions of computer users, making it a powerful ally for Sun in the idea of moving computing applications off desktop PCs and onto central servers. In addition, Google is a developer of AJAX, which gives Web browsers a more sophisticated user interface.

That networked vision, of course, would make Google more of a threat to Microsoft than it already is.

Office productivity software such as Microsoft Office is very different from the tools used for Web services tasks such as search, e-mail and Web site authoring, Schmidt said. But he added, “It makes sense from my perspective that these boundaries become less obvious as these technologies improve.”

Sun once had a Java-based version of StarOffice called StarPortal that was geared to run across the network. The product aimed to help a network service company compete more directly with Microsoft, but the company canceled it. Schwartz said he has no regrets: “Is AJAX or a browser an appropriate vehicle for heavyweight office productivity software? Absolutely not,” he said.

Mark Mahaney, an analyst for Citigroup Research, wrote in a research note that “for many years, Scott McNealy, the CEO of Sun Microsystems, talked about the network replacing the PC as the platform. In hindsight his pitch was much too early…However, today’s announcement indicates that perhaps the Internet can become the platform for applications delivery.”

For Google, the deal could boost revenue, Mahaney said. “The simple point is that a potential offering of a network-based application suite could lead to long-term incremental revenue for Google.”

The announcement appears to bolster the prediction made by Stephen Arnold, author of “The Google Legacy: How Google’s Internet Search is Transforming Application Software” that Google aims to become a hosted applications provider.

“This is the first step on the road that leads directly to Google and Sun trying to take Microsoft’s application and server revenue,” Arnold said in an interview. “It’s the foothills expressway to money; that’s the goal.”

The partnership will undoubtedly please the Unix developer community, he said. “The 40-year-old who really understands Unix and Solaris and doesn’t feel comfortable with the security vulnerabilities of a Microsoft Office. Suddenly there’s the promise of a new land ahead,” Arnold said.

Microsoft executives declined to comment on Tuesday’s announcement.