According to the documentation (look at the pre-installation docs for CC on the IP Office Documentation CD), you will need to use some flavor of IIS in conjunction with it. However, it doesn't expressly say that you can't use some other platform, so maybe you can. Only thing is, IPO is geared for Microsoft stuff, so I don't know how well it would play with Apache. Perhaps someone's written a 3rd-party app for it? May be worth a Google.