You might want to freely distribute your extension or make it available commercially, but how could you guarantee that the code is properly installed each time without having to do it yourself? And what about the updates or upgrades? Not all store owners are tech savvy or capable of changing files on their own.
Fortunately, Magento comes out of the box with its own package manager and extension marketplace called Magento Connect.
Magento Connect allows developers and solution partners to share their open-source and commercial contributions with the community and is not restricted to only custom modules; we can find the following types of resources in the Magento Connect marketplace:
Modules
Language packs
Custom themes