I looked there but it doesn't say where or how to download this "prerelease".
Joined: Dec 10, 2001
From that page:
We're now providing an early version of our 1.4 implementation, the Java 1.4 Developer Preview, to all seeded ADC members.
What a seeded ADC member is, I don't know. I'm not one of them. I'd guess that "ADC" stands for "Apple Developer Connection" or something similar. Visiting a shortened version of the aforementioned URL, http://developer.apple.com/ , indicates that it does indeed stand for "Apple Developer Connection". If I were interested in becoming a member of the ADC, then I'd likely click on the "Join Now" link.