I'm not sure what you mean by "mac front ends". OGo has some support for iCal.app subscriptions and publication. Though iCalendar-over-HTTP is not a protocol which is particularily well suited for calendars which can be written by multiple users. Hopefully Apple will support the CalDAV standard (still in draft) in one of the upcoming releases.

For simple needs an Apache WebDAV server (included in OSX) is sufficient to accomplish the same thing and installing a full OGo server is probably overkill.