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 websites via a hosting Control Panel. Although keeping the Operating System updated is not always considered fundamental, it can be a rather important task for a number of reasons. A more modern OS version could have better support for specific hardware, so you may get better performance for the websites and web applications which you install. Your server will also be more safe since updates often include security patches which deal with small issues that may enable unauthorized individuals to access your content. Last, but not least, current script versions, which are also released for both improved security and for additional features, might require a later version of the Operating System in order to work properly and with their full capabilities.