<p>I want to create a Java application bundle for Mac without using Mac.</p>

<p>According to <a href="http://developer.apple.com/documentation/Java/Conceptual/Java14Development/03-JavaDeployment/JavaDeployment.html#//apple_ref/doc/uid/TP40001885-208447-TPXREF120" rel="noreferrer">Java Deployment Options for Mac OS X</a>, I can do this by using Xcode, Jar Bundler, or from the command line. Once the files and folders are set up, all I need for the command line method is to call /Developer/Tools/SetFile. Is there a SetFile clone on Linux or Windows? If not, do I have to get a Mac?</p>

A Java application bundle on OS X is nothing more than a directory containing your .jars and a number of configuration files.  The SetFile tool sets a custom HFS filesystem property on the directory to tell finder that it is an app, but giving it a ".app" extension serves the same purpose.  I don't think there's anything stopping you from building one on, say, Windows, though of course you have no way of testing that it works, but if you are able to test it at least once on a real Mac, you could then conceivably update the .jars within it on Windows to reflect code changes without too much difficulty.
Have a look at the
Bundle Programming Guide
for more info.