This week, Skype finally released a version of its mobile application for Android phones. Unfortunately, the fine print revealed the new app was crippled, restricting U.S. users to Wi-Fi only calls, just as it had when the iPhone version was first launched.

But now, only days after the official Android app's debut, an ingenious developer has hacked the app to work over 3G. Here's how to use it on your own Android phone now.

Thanks to the guys at Engadget, we're pointed to the original forum postings for this unofficial version of Skype. But before you can use it - you'll need to enabled side-loading.

If you've never before side-loaded apps onto your device, you may be confused as to how to get started. Side-loading is one of Android's great features - it opens up the device for the installation of apps found outside of the Android Market. Of course, for novice users, this could be a security issue as it would allow the installation of apps from anywhere on the Web - and not all apps out there are safe. But if you're prepared to take on the responsibility of ensuring the security of the non-Market apps you install, side-loading is a feature worth enabling. And unlike the Apple iPhone, there's no need for advanced hacking like "jailbreaking" - it's just a setting you can switch off and on.

Step 1: Enable Side-Loading

To enable side-loading on your device, you'll need to go into your phone's Settings, then Application Settings. Tap the check box next to "Unknown Sources" to enable the installation of non-Market apps.

A pop-up warning message will appear, informing you that doing so makes your phone more vulnerable to attack and asks you if you agree to take responsibility for any damage to your phone or loss of data that may occur.

Unless you've changed your mind, tap "OK."

Step 2: Download the Skype APK

Now you need to download the hacked Skype APK file and copy it from your computer to your phone via your phone's memory card. You'll then use some sort of file manager application (like AndExplorer, ASTRO, Linda or others) to access the file.

Alternately, you can browse to forum user Xeudoxus's original post from your mobile and tap the link to the Skype APK.

Once installed on the phone, you run it just like any other application.

That's it!

Note: Side-Loading Workaround & Additional Info

As noted on Engadget, some Android phones don't allow direct side-loading of apps, for example, the HTC Aria. For those users, there are alternative ways to install apps, but it's more complicated than just tapping a link on the Web.

One option is the Android Central Sideload Wonder Machine, which is a program for Windows computers that transfers apps from PC to phone. More info on that program is available here on Android Central.

Remember, too, that Skyping over 3G uses data, so be aware that you don't go over your data plans limits. ReadWriteWeb is not responsible for your phone bill - proceed at your own risk.

And it may be stating the obvious to say this, but this is not an official version of Skype - so you may not want to show it off to the guy at your carrier's store when you drop by for tech support, for example.

One final note: Verizon users have no need for this hack because Skype partnered with Verizon in March. The Verizon version of Skype has had 3G calling from the start.