If you get a server of your own, it will work independently, so it will have its own Os and you could later install server side applications directly or script-driven websites via a hosting Control Panel. Though keeping the Os updated isn't always considered an absolute necessity, it can be a very important task for a variety of reasons. A newer Operating system version could have better support for specific hardware, so you could 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 take care of small issues that may permit unauthorized individuals to access your content. Last, but not least, current 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 full capabilities.