From Deep IT:
Submarine is an easy-to-use software self update framework for Cocoa developers. It was developed by Deep IT and it is absolutely free for any use (open source & commercial) on one condition: you must refer to Deep IT with publisher's URL in your product at a visible place. This project is designed to simplify the software update process. If you need some exotic stuff like tar, bz2, gz, bz archives, or DMG disk images, please, use Sparkle. For the sake of simplicity, we deal only with APP bundles in ZIP archives. Submarine framework is not an open source product, however you are free to send us your suggestions at any time. The SubmarineDemo project shows you how easy it is to integrate the Submarine framework with your products. There is only one major limitation: your application should come as a simple .app bundle (i.e. without an installer.) However, you can perform some post-install operations using delegate methods.
Version 1.2 features better icon handling in host products' files.