If you get a server of your own, it will work 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. Although keeping the Operating System updated is not always considered fundamental, it can be a rather important task for several reasons. A more modern OS version could have better support for certain hardware, so you may get better performance for the websites and web apps you install. Your server shall also be more safe because updates usually include security patches which take care of small problems that may enable unauthorized people to access your content. Last, but not least, more recent script versions, which are also released for both boosted security and for additional features, might require a later version of the Os in order to work properly and with their 100 % capabilities.