Yesterday, we saw Apple release iOS 5 beta 6 to developers who have UDID registered iPhone, iPad and iPod touch. Basically, iOS beta firmware is only intended for developers and can't be installed if you don't have a Developer Account which costs $99 per year. Don't worry though, the workaround that we are documenting below will teach you exactly how to install iOS 5 beta 6 without UDID registration or even a Developers Account. 
iOS 5 beta firmware ipsws are only available for developers in the Developers Portal. However, soon these ipsws make their way on to file sharing websites on the internet so that anyone with an iDevice can get access to beta firmware, but most people don't know that you need to have your device UDID registered with a Developers Account in order to run iOS beta firmware on it. If you're wondering where you can find the UDID of your device, follow this tutorial.
Many budding beta testers try to buy UDID registrations off the internet, but Apple is now closing accounts of those developers who sell UDID registrations and are also flagging all UDIDs registered with their accounts. If you're that desperate for a UDID registration, you may try out your luck with us as we have been offering free UDID registrations for iPhone, iPad and iPod touch.
On the other hand, if a UDID registration is not what you are looking for, simply follow this tutorial to install and activate iOS 5 beta 6 on iPhone, iPad and iPod touch without a Developers Account. This procedure will eliminate the this device is not registered as part of the iphone developer program error which is displayed if you install beta firmware on a device that doesn't have its UDID registered.
How To Install iOS 5 Beta 6 Without UDID Registration Or Developers Account:
Step 1: Download the following: Download iOS 5 beta 6 ipsw for iPhone, iPad and iPod touch Download iTunes 10.5 beta 6 for Windows and Mac Download i-Funbox for Windows or iPhone Explorer for Mac (Google is your friend)
Step 2: Once you have downloaded iOS 5 beta 6 ipsw for your device on the computer, follow this guide to install iOS 5 beta 6 on iPhone, iPad and iPod touch. When installation completes, don't do the PC-free iOS 5 setup. You first need to jailbreak your device.
Step 3: Follow the tutorial to jailbreak iOS 5 beta 6 tethered using redsn0w, on Windows and Mac. This won't work on the iPad 2. Jailbreak is mandatory because we need access to the root filesystem of the device.
Step 4: After the jailbreak has been done, we now have to delete a certain key and string from within the filesystem to install iOS 5 beta 6 without UDID registration. To do this, you may download i-Funbox or iPhone Explorer, depending upon what computer you use. Step 5: After you have downloaded and installed the relevant software for your Windows or Mac computer, connect your device to the computer and launch the software. Using the software, navigate to this path: filesystem/library/coreservices/systemversion.plist. After locating this .plist file save it to your desktop.
Step 6: Once saved to the desktop, right click and open this .plist file in either Notepad or Text Editor. Now locate this: <key>ReleaseType</key> <string>beta</string> and remove it. Save changes to the file.
Step 7: Copy this file back to its original location in the filesystem of your device running iOS 5 beta 6. Close the software and reboot your device. That's it! You have successfully installed iOS 5 beta 6 on your device without needing a UDID registration or a Developers Account. Your device will sync flawlessly with iTunes and you will be able to use all of the service without facing that ruddy this device is not registered as part of the iphone developer program error. Don't install stock iOS 5 beta firmware on your iPhone if you rely on a software unlock. You will lose your unlock and won't be able to access cellular services on your iPhone 4 or iPhone 3GS.
If you have a factory unlocked or carrier locked iPhone, you can install iOS 5 beta 6 if you want to. Any questions? Seek help from our experts by simply leaving a comment down below.
Editor's Note: It appears that most of you are facing issues while booting iOS 5 beta 6 tethered on your device. To fix this problem, the iPhone Dev Team is going to release redsn0w 0.9.8 beta 6 in a couple of hours and we'll let you know when that happens. Once that happens, the procedure in this post is what you need to follow in order to install iOS 5 beta 6 without UDID registration. Keep checking back here for the update.
UPDATE x1: iH8sn0w has released sn0wbreeze 2.8 beta 6 for Windows which not only jailbreaks iOS 5 beta 6, but also removes UDID check and beta timer, allowing you to install iOS 5 beta 6 without needing a Developer Account. Details, download links and tutorials posted here.
UPDATE x2: iPhone Dev Team has released redsn0w 0.9.8 beta 6 "JetBlue Edition" with support for iOS 5 beta 6 tethered jailbreak on iPhone, iPad and iPod touch. Follow this guide to download and jailbreak iOS 5 beta 6 using redsn0w 0.9.8b6 on Windows and Mac. Then if you want to install iOS 5 beta 6 without UDID registration or developers account, simply follow all of the steps given above.