"We think the JCK is the greatest thing since sliced bread," said Sun's Graham Hamilton last week, referring to the Java technology Compatibility Kit. "It isn't necessarily perfect, but it's been a great vehicle for driving real compatibility," he added. He was speaking as Sun released the complete J2SE compatibility test sources under a read-only license, "so that the community can see what's really going on with Java compatibility testing."

In order to keep the license simple, explained Hamilton, Sun has restricted it to be strictly "read only."

"I want to emphasize this," he continued. "The license does not allow you to compile or run the tests.... We did this because otherwise the license would have blossomed into a twenty page legal document. But we have tried to make sure the license meets the reasonable needs of developers who want to evaluate the JCK sources."

Any developer who wants to move beyond reading the tests to actually compiling or running tests, will need to move to one of the fancier and more complicated licenses such as SCSL or the upcoming J2SE Java Distribution License (JDL), added Hamilton, a VP and Fellow in the Java platform team at Sun.

"But if all you want to do is look at the tests, these licenses are definitely total overkill, which is why we've created the new read-only license to allow simple evaluation access."

"The Java team at Sun takes compatibility really seriously," wrote Hamilton in a blog accompanying the announcement. "Personally, I'm happy to be a deranged lunatic on this issue. Other people have their own particular obsessions about software licensing, but our obsession is around preserving compatibility."

The complete J2SE compatibility test sources can be found at: http://jck.dev.java.net

• Refactoring: Best Thing Since Sliced Bread?