I have Ubuntu 12.10, and it is not a Ubuntu server version. for installing Directadmin, Do i need Ubuntu server or i can install it on my own Ubuntu?
Ubuntu Server is just a set of default packages to be installed using a text-based installer, it's not another OS. The most important difference here is a more tweaked kernel for servers, while the Ubuntu desktop flavour comes with a kernel tweakers for desktop usage. The whole user space is exactly the same, the availability of packages is the same, etc.
So, in short, yes, provided the software runs on the Ubuntu release, it will just work independently of whether you have installed Ubuntu from the desktop installation or the server installation. This applies to any application you want to run in Ubuntu.