This is the big one, Elizabeth: Sun Tuesday filed a breach of contract lawsuit against Microsoft Corporation, charging that IE 4.0 violates the Java licensing agreement the two companies signed last year. Sun is alleging that Internet Explorer 4.0 failed to pass its Java Development Kit (JDK) 1.1 compatibility tests and that Microsoft is deliberately misleading developers and violating a Sun trademark.

IE 4.0 failed the compatibility tests because Microsoft did not include support for Sun's Java Native Interface (JNI) and Remote Method Invocation (RNI) APIs. Sun claims that Microsoft has also altered some of the core Java APIs by hiding Windows-specific calls into Sun's Java class libraries.

The trademark violation occurred when Microsoft used the Java compatibility logo without passing the compatibility tests needed to earn the logo. Sun is attempting to prevent Microsoft from using the Java logo, but even if the logo were removed, Microsoft would still be in breach of contract for not supporting all of Sun's APIs.

Microsoft's answer was swift.

"We have not yet seen the complaint, but based on the accounts we have seen, Sun's claims are outrageous," said a release from Microsoft. "Microsoft has delivered the most compatible implementation of Java on the marketplace and is well within the terms of our agreement. Reviews consistently state that Internet Explorer 4.0 delivers the fastest, most functional and most compatible implementation of Java on the market. Sun has no ability to impact the shipment or deployment of Internet Explorer 4.0. Sun has apparently decided that they can't compete in the marketplace. We think the evidence will show that Sun has repeatedly failed to live up to its obligations to Microsoft. Since this is a matter now in active litigation, we will not be speaking about the details of the case in the press.