It shouldn't matter, as long as they're on the same internal network.
You just have to know the internal ips for each machine and they have to be in the same network. They might be something like 192.168.x.x. So the mac is running a server with, let's say, IceCast (doubt there's a build for mac though, you might have to compile it yourself). If it had the ip of 192.168.1.5, then any machine on your network (with the beginning address of 192.168.1.x) with programs that can accept streams, like WinAmp or Windows Media Player, just have to connect to 192.168.1.5:8000 (8000 is the default port that IceCasts uses to stream) and it should start receiving the stream.
Not sure how experienced you are so sorry if I said it would be easy with the link to the tutorial if you're not used to entering commands. You can make VLC stream something from the gui. It has something where you can access broadcasts..