The release notes for Xcode 2.1 state:

WebObjects 5.3 The WebObjects developer tools are now included with the Xcode Tools. For more information see here.

• EOModels can now be edited within Xcode with a new EOModeler plugin that integrates CoreData modeling tools.
• WebObjects Builder has UI enhancements and generates HTML 4.0.1 code.
• WebObjects Runtime now supports HTML 4.0.1.
• NSArray, NSDictionary and NSSet now implement the java.util.Collection interfaces.
• Axis 1.1 has been integrated with the Direct To WebServices feature.
• WebObjects is qualified against Oracle 10g using the 10.1.0.2 jdbc drivers.

In addition to:

• NOTE: You do not need a previous version of WebObjects on your system before installing WebObjects 5.3

Whoo hoo! Doing a happy dance now!