Linux DMZ in a Windows Network

I'm a wet-behind-the-ears reluctant sysadmin, so I'm playing catch-up here. I've come across the term DMZ before, but I never looked into it until just recently. In fact I'm still not sure exactly what's involved; I'll be continuing my studies and test projects.

But suffice it to say I like the idea.

I have a small-business customer for whom I'd like to implement the concept. He's running WSE 2012 R2 with a handful of client machines/VMs.

The trouble is that he won't want to justify the cost of a Server 2012 R2 license, especially for this sole purpose in his small domain.

So my question is this: will I be able to use a non-domain-joined instance of CentOS (for example) running in a VM for his DMZ?