The last few years have seen the rise of closed platforms — operating systems that only allow you to install software approved by the operating system’s developer. However, many popular platforms — even mobile ones — are still open platforms.

Platforms with app stores can be considered open platforms if they allow you to install apps from outside the app store, a process referred to as “sideloading.” Even if a platform has a restrictive app store, sideloading could allow users to exit the walled garden if they so choose.

Under the US DMCA and similar laws elsewhere in the world, jailbreaking to escape a closed platform and install unapproved software is considered a crime. It’s the same law that makes it illegal to watch DVDs on Linux. (The US DMCA actually makes an exception for jailbreaking smartphones, but not tablets or other devices.)

Windows Desktop: Open on Intel, Closed on ARM

The Windows desktop is the most popular open computing platform among average computer users, and Windows’ open nature has allowed Windows to be a platform for innovation. No one needed to ask Microsoft for permission to distribute Windows desktop software — they could write their own software and distribute it directly to users.

On standard Intel x86 editions of Windows 8, the Windows desktop is still an open platform. You can install anything you want on it. Microsoft has no say.

On ARM Windows RT machines, the Windows desktop is now a closed platform. Only applications developed by Microsoft are allowed on Windows RT’s desktop. Current rumors suggest that Microsoft is working on creating a version of Microsoft Outlook for Windows RT. Microsoft is the only company allowed to create and distribute new applications for Windows RT’s desktop. People who want new desktop applications (such as an email client) for the Windows RT desktop have to ask Microsoft for them.

Windows Modern: Closed

Windows 8’s new Modern interface is a closed platform. Average people can only install Modern software from the Windows Store. If Microsoft removes an app from the Windows Store because it violates any of their guidelines, you won’t be able to install or run it on your system. In other words, Microsoft exercises a veto over the Modern apps you can run on Windows 8.

Like many other closed platforms, Microsoft allows sideloading, but only for developers (to test their own apps), and corporate networks (to use internal apps). Sideloading is designed so that average users can’t use it for plain-old unapproved apps.

Apple Mac OS X: Open

Apple’s Mac OS X is still an open platform. Apple’s Mac app store places various restrictions on developers and subjects their apps to sandboxing, but developers can choose to leave the app store and distribute their software directly to users. The Mac app store isn’t the only game in town, as it is on Apple’s iOS.

Mac OS X has a setting that restricts installation of apps from outside the store, but it can be toggled on and off by the user.

Linux & Google Chrome OS: Open

Linux is open-source and decentralized, so of course you can install anything you want on it. Chrome OS is based on Linux, and offers the same freedom. You can enable developer mode and install Ubuntu and other software alongside your Chrome OS system

Chrome can only install web apps and extensions from the Chrome Web Store by default. However, there’s still a way to install apps and extensions from outside the store.

Apple iOS: Closed

Apple’s iOS is the most widely-known closed platform. iOS users can only install software from the app store. When Apple removes an app from its app store, it’s banned from the iOS platform instead of being available elsewhere. Apple has put many restrictions on developers throughout the years, once banning the distribution of any app that competed with Apple’s included apps, blocking the Google Voice app for a year, and banning various games that deal with serious political issues (graphic violence is okay).

iOS does allow developers and businesses to sideload their own custom apps, but not average users.

Google Android: Open

Google’s Android operating system is an open platform. Android is configured to only install software from Google Play by default, but users have the ability to check the Unknown sources checkbox in Android’s settings. This enables the installation of Android apps from outside Google Play.

Windows Phone: Closed

Microsoft’s Windows Phone takes an iOS-style approach where you can only install apps from the Windows Phone Store. This replaces Microsoft’s previous approach with Windows Mobile, which allowed you to install software from anywhere you liked. Windows Phone has more in common with the Modern environment and its restrictions than the open Windows desktop.

BlackBerry: Open

BlackBerry devices also allow you to install apps from outside BlackBerry’s app store. This is particularly useful on BlackBerry 10 devices, where you can sideload the hundreds of thousands of Android apps that haven’t been officially ported to BlackBerry.

Game consoles are becoming computing platforms in their own right, with apps and browsers in addition to games (which are just another type of software). However, popular game consoles have been closed platforms for a long time. Consoles as old as the original Nintendo Entertainment System (NES) required game developers to license their games with the console’s manufacturer before the can be distributed and run on the console. The “homebrew” scenes available for various game consoles often exploit security bugs in a console to run unapproved, homemade games.

The Android-powered Ouya and PC-gaming-powered Steambox consoles will offer open platforms where anyone can develop games and distribute them directly to users without requiring the manufacturer’s approval. In the meantime, the PlayStation, Xbox, and Nintendo consoles are currently all closed platforms.

So why should you care? Well, open platforms allow us the freedom to decide what runs on our own computers (including smartphones, tablets, and game consoles, which are all computers in their own right) without becoming criminals. Even if jailbreaking wasn’t a crime, the fact that a platform is open allows developers to easily distribute software that a platform’s controller might not like.

Image Credit: Mark Fischer on Flickr, Richard Gillin on Flickr, Kiwi Flickr, Jeff Geerling on Flickr, Blake Patterson on Flickr, Jon Fingas on Flickr, Jon Fingas on Flickr, Darien Library on Flickr