Ubuntu – Uploading apps to the Ubuntu Software Center

Packages that are submitted for extras.ubuntu.com cannot install binaries that are intended to be accessible from the default $PATH - they are meant to be relatively lightweight GUI applications. This excludes installing Upstart services or other files into /etc.

The restrictions on files were made for security reasons when the ARB process was written up.

For applications such as these, you can still submit them to the Ubuntu archive (main, universe) & request a backport to the stable release.

The clause is meant to inform you, the developer, that it is your responsibility (obligation to use that terminology) to ensure your application runs on the supported versions of Ubuntu, not Canonical's. You are not forced to test on all versions, but it is in your best interest to ensure it runs on the latest Ubuntu release and prior versions.

For the purposes of the software center and paid applications, you should test 11.10, 11.04 and 10.10. You always have the option of only supporting the latest version if you wish and just need to inform the reviewer of that requirement when submitting your application.

In the case of ARB apps (FLOSS apps) you will want to ensure compatibility with all supported releases.

I hope that helps clarify the terms a bit better.