We could definitely do it this way -- check to see if the themes.jar file already exists each time build it dynamically if it's not there. I agree that technique is a little cleaner. I don't feel strongly about it at all, but I'd of course be more than happy to integrate a build.xml patch if you really would like it to change =). I guess to me it's an issue that comes up so rarely that I'm not that concerned with it.