If you get a server of your own, it will operate independently, so it'll have its own Os and you could later install server side apps directly or script-driven internet sites via a hosting Control Panel. Though keeping the Os updated isn't always considered a necessity, it can be a really important task for several reasons. A more modern OS version could have better support for certain hardware, so you might get better performance for the sites and web applications you install. Your server will also be more safe because updates typically include security patches that resolve small problems which may enable unauthorized individuals to access your content. Last, but not least, more modern script versions, which are also released for both increased security and for additional features, might require a later version of the Os in order to work correctly and with their 100 % capabilities.