When you bring up a Java 1.4 application, you'll see the button hierarchies and so on and can make calls into your Java application from AppleScript. In addition to making your Java applications AppleScriptable...
The difference between GUI scripting and AppleScript is the difference between screen-scraping HTML and a web services API wired up to business logic. Yes, the latter requires more work on the developer's part, but the former is a dreadful hack, sure to break the next time the scrape-victim trivially changes its spots.
AppleScript is not a macro language, so GUI-scrapable application is not an AppleScriptable application. I realize the distinction is a bit peripheral to Java (making a bona-fide Java app legitimately scriptable sounds like tilting at windmills) but for Mac developers, it's anything but. I have a lot of fear that we're going to see GUI scraping as an easy way to slap a "scriptable" label on halfassed applications.