US District Judge Frederick Motz approved a preliminary injunction sought by Sun that forces Microsoft to upgrade its operating system and browser products with Java software that uses the latest version of the technology.
Microsoft will appeal the ruling, said Jon Murchison, a legal spokesman for Microsoft.
"We are disappointed with today's ruling and still need to review the details of the decision," he said. "After our initial review, we do intend to appeal this injunction and will ask the appeals court to hear it on an expedited basis."
Serious risk In a 42-page opinion, Motz sided with Sun, noting that without Microsoft adopting the most recent version of the technology, Java will not be able to compete fairly against Microsoft's emerging .Net initiative.
"Unless Sun is given a fair opportunity to compete in a market untainted by the effects of Microsoft's past antitrust violations, there is a serious risk that in the near future the market will tip in favour of (Microsoft)," Motz wrote in his opinion.
"Sun's potential harm is great if the injunction is not granted. Microsoft's potential harm is slight if the injunction is granted," he continued.
Sun had asked the judge to force Microsoft to distribute a Sun-authorized Java Virtual Machine, or JVM, and to discontinue an older Microsoft version currently in use. The preliminary injunction will stand pending the final outcome of a private antitrust lawsuit filed by Sun against Microsoft.
The judge has yet to issue an order on how to enforce his ruling. Lawyers from Sun and Microsoft are expected to meet with Motz over the next two weeks to determine how Microsoft will adhere to the ruling. It is slated to go into effect within 90 days.
Victory for consumers The antitrust suit, filed in March, charges that the software maker used its monopoly in the market for PC operating systems to thwart the adoption of Java. That case is expected to go to trial next year and last as long as two years, according to Sun legal counsel Lee Patch.
Sun applauded the judge's decision, calling it a "victory for consumers" who will be able to buy Windows machines running the latest Java technology, as well as a boon for Java developers who can ensure that applications they build will run on Windows PCs, Sun said in a statement.
The ruling is also expected to benefit Sun, which relies on the wide adoption of Java to win developer support and sell its high-end server products, said Richard Green, vice president and general manager of Sun's Java division. For one, the updated Java support will allow Windows users to run Java-based Web services.
"The availability of a Java-powered Web services network will create a lot of interest" in Java-based server products, Green said.
Fragmentation Earlier this month, Microsoft and Sun presented three days of oral arguments related to the injunction in the US District Court for the District of Maryland in Baltimore. During those hearings, Sun told Motz that Microsoft has tried to fragment the Java platform by distributing its own JVM, which Sun says is incompatible with its own Java products.
Microsoft argued in its defence that US District Judge Colleen Kollar-Kotelly has already struck down a similar request to include Java with Windows during the remedy hearings in the US government's antitrust case against Microsoft. The company also said Sun could ensure wider Java adoption by investing money to develop its own network for distributing the technology on desktop computers.
Motz shot down that argument in his opinion, writing, "evidence makes clear that Sun could not eliminate the risk of market tipping by investing heavily to develop distribution channels if its investment achieved only widespread, rather than near equal, distribution of Java."
Microsoft has stated that its .Net technology will be shipped in nearly all of its desktop and server software products.
Motz is coordinating and presiding over a number of private antitrust cases as well as numerous class-action lawsuits that have been filed against Microsoft.
(Marc Ferranti in New York contributed to this report.)