Really about anything will run it for a small group of people.
What you need to look at is your os choice.
For windows, the minimum visual studio requirement is 2012 - which requires windows 7 to compile. (It can be targeted for older os's..but, don't ask me how to do that :P )
Linux, I have no idea... Someone with that expertise will need to chime in.
EDIT: If the group is small enough, you can probably host/play on the same machine.
Uleat of Bertoxxulous