HTC recently changed their policy. They would sell phones with locked bootloaders. But would provide an option to unlock them. By unlocking them you would agree to terms and conditions which basically requires you to void your warranty. technically speaking unlocking any locked phone would automatically void the warranty. not sure if indian service centers are capable of detecting this process. not sure if the process can be reversed. unlocking the bootloader is required to install custom ROMs on your phone. if you are happy with whatever version the company has loaded on the phone, it does not matter to you. but the problem arises if the company decides to not release newer android builds for the phone you have.