However, the order provides only a partial victory for Sun. The court rejected a motion filed by Sun to reinstate the injunction based on copyright law, referring instead to California's unfair competition statutes.
The distinction is an important one for Microsoft, which has argued from the start of the case that its disagreement with Sun is a contract dispute. Copyright violations presume that a plaintiff has suffered irreparable harm, while contract law requires harm to be proven in order to obtain an injunction.
"This strikes fundamentally at the heart of Sun's position in this case and supports Microsoft's oft-stated position that this is a contract dispute between two large and sophisticated companies," Microsoft said in a statement.
Nevertheless, Sun also claimed victory from the mixed ruling, asserting that the order issued by Judge Ronald Whyte, of the US District Court in San Jose, California, is a win for Sun, software developers and the general public.
"As we have said from the start of this case, Microsoft's misconduct with respect to Sun's Java technology has harmed competition, as well as those who use and rely on the Java technology," Michael Morris, general counsel, Sun Microsystems, said in a statement.
The dispute between the companies stems from a complex Java licensing agreement that Microsoft signed with Sun in 1996.
The following year, Sun filed a copyright infringement and unfair competition lawsuit against Microsoft, claiming the software giant used a "polluted" version of Java in its products that encouraged developers to write programs that run only on Microsoft's Windows operating systems. Microsoft did this, according to Sun, because the vendor saw Java's cross-platform capabilities as a threat to Windows.
Microsoft has maintained that it stuck to the letter of its licensing agreement, and merely offered developers the choice of writing more feature-rich Java programs that take advantage of features specific to Windows.
In November 1998, finding that Sun was likely to win its case based on the merits, Judge Whyte issued a preliminary injunction forcing Microsoft to alter the Java technology in its products in order to pass Sun's compatibility tests.
In a surprise development last August, a US Appeals Court overturned Whyte's injunction on the grounds that the California judge had not explained clearly why he had chosen to treat the case as a copyright infringement dispute.
The order grants Sun's request to reinstate the injunction under an unfair competition provision of the California Business and Professions Code, but rejects a separate motion filed by Sun to reinstate the injunction under copyright law.
The terms of the preliminary injunction are similar to those of the original injunction granted in November 1998, and prevent Microsoft from performing the following actions:distributing operating systems, browsers or development tools that fail to pass Sun's compatibility tests; failing to warn developers that Java programs written using Microsoft's incompatible toolkit will run only on Microsoft's Java implementations; andfalsely advertising that Microsoft's incompatible Java products are compatible with the specifications for the Java technology, or are endorsed by Sun.
Microsoft said the ruling "doesn't alter the status quo" since the vendor had never reverted to using its original, incompatible version of Java after the appeal's court overturned Whyte's injunction last summer.
The software giant also noted that Whyte was clear that "nothing in this order requires Microsoft to recall any product" and "this order does not prevent any purchaser of Microsoft's products from continuing to use them."
No trial date for the lawsuit has been set.