A three-judge panel sent the case sent the case back to U.S. District Judge Ronald Whyte for further consideration.
Whyte's ruling held that Sun was likely to prove that Microsoft's Java products violated Sun's copyrights. Whyte, of San Jose, California, found that the omission of a technology known as JNI, or Java native interface, kept Microsoft's Java from passing a compatibility tests required in its licensing agreement with Sun.
The order required Microsoft to immediately add the technology and make other changes while the case continued.
Microsoft had argued that the decision harmed Microsoft customers by allowing them access to only one version of Java and depriving the public of innovations Microsoft had legally made to Java. They also argued that Whyte applied standards based on copyright law in justifying the injunction when in fact the standard should have been based on contract law.
Sun has billed Java as a language that will run on many different computers, regardless of the operating system they use. The company sued Microsoft in 1997 accusing it of intentionally trying to thwart Java's "write once, run anywhere" promise by shipping incompatible versions with its widely distributed Internet Explorer.
The Justice Department and 19 states have echoed similar charges in Microsoft's antitrust trial, arguing that the software giant illegally sought to protect a monopoly in operating systems by killing Java's cross-platform ability. Microsoft has vigorously denied those charges.