If you purchased your software from a retailer, you will be prompted to register each time you open the program. TurboTax requests that you register your software just in case there are any program issues that may affect your taxes. However, you are not required to register, just click on "Continue" to get past this section.
If you are using an online version of TurboTax, the program will ask you to register your account. Before you can file your tax return, you will need to register your account. You can skip this section until you are ready to file by clicking on "Continue."