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 applications directly or script-driven websites through a hosting Control Panel. Though keeping the Operating System updated isn't always considered an absolute necessity, it can be a rather important task for several reasons. A newer Operating system version might have better support for certain hardware, so you could get better performance for the websites and web applications which you install. Your server will also be more safe as updates normally include security patches which take care of small problems that may allow unauthorized people to access your content. Last, but not least, newer script versions, which are also released for both boosted security and for additional features, might require a later version of the Operating System in order to work correctly and with their 100 % capabilities.