The offline version can also combine files whilst minifying and obfuscating js and css files too.
So to use in netbeans builds do this:-
1) Download the offline version from here,
2) Put it in your ant lib directory, windows default for nb 6.5 is
C:\Program Files\NetBeans 6.5\java2\ant\lib
3) For js combining, choose an include file name say compressed.js and use this as the include in your html/jsp files.
4) add something like the following to your project build.xml substituting the filename for your own:-
Job done, this has saved the overhead of 3 JS files by combining into one, making them smaller and obfuscating them, all automaticly in the build process.
Works a treat.