This application, officially provided by Oracle (previously Apple), acts as wrapper that starts a JVM with a set of options. Jar2app relies on JavaAppLauncher (although you don't need to install anything). This will install the jar2app application/script and make it available for you to run. It will install to /usr/bin, but you can change this by passing your desired prefix to install.sh, as an argument. Just clone the repository and run install.sh, or uninstall.sh to remove it.
For more information on how to submit bundles to the appstore, see here and here. This is not a limitation of jar2app, it's just how the Appstore requires you to do things. Jar2app may bundle your jar, but there are several steps you further need to take to submit your application to the Appstore. If you think that's just a strong case of NIH, feel free to grab what you want from me and send a patch to the other projects :) Just follow the GPL! Can I submit bundles created with jar2app to the Appstore? The solution I was left with was just rolling out my own. Most of the other alternatives require third-party tools that embed other functionality and which simply cannot be stripped.
Packr uses a custom launcher and is meant to pack things for Mac OS X, Windows and Linux. If you're also considering why these contributions weren't just sent to one of the other projects, it is because this could not be done easily. Really, isn't it wonderful to have such an easy-to-use interface? jar2app, however, tries to keep the power of those utilities while providing high simplicity in the process. Most solutions out there require a gazillion arguments, or installing ant and memorizing lots of conventions. However, this project was born out of the need to do something easily and without much cruft. I acknowledge them and even have several links to them. (TOC created with the help of gh-md-toc) Aren't there other tools that do this? Why another one?