If you get a server of your own, it will work independently, so it'll have its own Os and you can later install server side programs directly or script-driven sites through a hosting Control Panel. Even though keeping the Os updated is not always considered fundamental, it can be a rather important task for a variety of reasons. A newer OS version may have better support for specific hardware, so you might get better performance for the internet sites and web apps which you install. Your server shall also be more secure since updates typically include security patches which fix small issues that may permit unauthorized individuals to access your content. Last, but not least, newer script versions, which are also released for both improved security and for additional features, may need a later version of the Os in order to work properly and with their full capabilities.