Do you want to get iOS 9 now and not want until the public release? If you do, there is good news for you. This post will teach you how to download and install iOS 9 betas for free without a UDID. Also if you would like a more in depth tutorial go here: besttechinfo.com/install-ios-9-beta-1-free-without-udid/
First step is to make sure your computer has the latest version of iTunes. If it doesn't you will get an error code and fail. You need your iDevice to be on the latest public firmware. After that download iOS 9 beta 2 for your device. Go to imzdl.com/ios.html to download iOS 9 betas. Once you're done downloading the beta version, plug in your iDevice and open iTunes. On Windows hold shift and click Check for Updates (Mac-hold the option key) and find and select the file you just downloaded (if it downloaded as a .zip file unzip it first). The rest of the process will happen automatically.