Since iOS 2, users have only been able to use their iDevice the way Apple tells you do. They did not allow you to customize your device, or change the system. The only thing you could do is install apps, all of which require Apple's approval and therefore cannot change your system. Users have been able to make their device open themselves by a process called 'jailbreaking' for years, but this should be a standard feature.
This petition is NOT asking Apple to change their app aproval process, but to at least allow the major alternate app store (Cydia) to be installed, and possibly other minor alternatives. With this, users can change any part of their system, and customize THEIR device how THEY want to.
This peitition is aimed at Apple to get a more open iOS. An iOS where users can do anything they want with their device. After all, you did buy the device, so it is yours. Make sense?
If this peition goes as planned, no more limitations on what you can do with it, at most just warnings that you are on your own. Apple will recognize that once we buy the device, it is ours. We can do whatever we want for it, within legal boundaries.