I'm running it on windows to work on a mod for it. I just have to use my hosts file to get it to point localhost for the domain its registered to. But thats simply to run a duplicate so I'm not tinkering with my pristine setup on the net, even though I'm not live with it yet. But it does work.
Modernbill is a great peice of software for billing but leaves a bit to be desired if you are going to be using it for game hosting which I assume you are. You might look into a program called 'Kronos' (kronos-cp.com) which is a game server control panel but has a built in billing center as well. So you can use it for double duty Difference is it was built for game server companies where modernbill was tailored for webhosting so alot of the nice features you wouldn't use anyway.