Unfortunately, I think your system is underpowered for what you are looking to do.
Looking at system requirements, we know that Windows Server 2012 R2 has a minimum requirement of 32 GB disk space and 512 MB RAM, and the client-oriented Windows 8 needs at a minimum 16-20 GB of disk space and 1-2 GB RAM depending on processor architecture.
Note that these are minimum requirements; in practice, you will likely want to at least double these figures. Consider that for Windows 8, while the minimum requirement for RAM is 1 GB on 32-bit and 2 GB on 64-bit, on both architectures the recommended minimum is 4 GB RAM. I have a 32-bit Windows 8 (just now upgraded to Windows 10) virtual machine that I have given 3 GB RAM; that one is sluggish, but usable, and it does not run any heavy software.
Normally for a situation like yours, I would suggest looking at virtualization. However, virtualization of, in your case, a single running Windows instance would consume, at a minimum, more than three quarters of your total available storage and a sizable chunk of the available RAM.
Even if we forget about running the two operating systems concurrently and accept having to reboot from one to the other to switch tasks, you still need the disk space to store the operating system, software, and any applicable data files. No matter how you slice it, even just the operating system itself is going to use up a large fraction of that 40 GB SSD. And because Windows and Linux can't use the same file systems, you will almost certainly have to repartition the drive.
And that amount of data is before we have even installed the game server software, much less started it.
You could probably get away with an either/or situation with the hardware you have, but not both, even in a dual-boot configuration. Depending on what you are using that Linux system for, it's doubtful that both of these would even fit on the storage that you have. If you have more than a few gigabytes total used on the Linux side, you'd need to bring out the shoehorn to make everything fit.
If you want to use that server, start by installing some more storage, and perhaps add some more RAM. I would probably want to add another some 40-60 GB of storage and an another 4-8 GB of RAM. Then look at virtualization software such as VMware or VirtualBox (depending on your needs).