If you get a server of your own, it will operate independently, so it will have its own Os and you'll be able to later install server side apps directly or script-driven sites via a hosting Control Panel. Even though keeping the Os updated is not always considered a necessity, it can be a very important task for a variety of reasons. A more modern OS version could have better support for certain hardware, so you could get better performance for the internet sites and web apps that you install. Your server will also be more safe as updates typically include security patches which fix small problems which may enable unauthorized individuals to access your content. Last, but not least, more modern script versions, which are also released for both improved security and for additional features, might require a later version of the Os in order to work correctly and with their 100 % capabilities.