Try checking out ical rather than iCal.
That is ical from X11 contrib.

Completely different sharing method.

On Fri, 26 Jul 2002, Bob Tanner wrote:

> New thread, so it can be disassociated with the trolling of the parent thread.
> 
> The whole linux replacement for exchange problem has been a thorn in Real Time's
> side for a very long time. And from the heated debate on the parent thread I
> guess others are feeling the "thorn" too.
> 
> I swear our sales guy (hi Dennis!) asks me weekly if we have a -complete- linux
> solution for exchange.
> 
> So, here I'll start a constructive thread to discuss solutions. Below is a post
> from Nate that is a good start:
> 
> >>On Wed, Jul 24, 2002 at 10:15:48AM -0500, Christopher A. Gahlon wrote:
> >> Help!!!  The CEO has just mandiated unified calendaring/scheduling for our
> >> company.  And unless I can find a viable alternative he says I'll be stuck
> >> supporting exchange and outpuke.
> >
> >I haven't checked this out, but this was announced in April by Sendmail.
> >
> >They now have a Calendar server.
> >
> >http://store.sendmail.com/cgi-bin/smistore/e.store/prodcategory.jsp?BV_UseBVCook+ie=Yes&prodCategory=-9343&localId=USA
> 
> I think the hardest part of replacing exchange is the shared calendaring. So,
> how about some links and discussions on productions/solutions that implement the
> iCal protocol?
> 
> Sendmail Calendar Server I've seen, but there problem is listed below:
> 
> Systems and Standards Supported
> 
> Platform Availability: Sun Server running Solaris 8
> Required Software: Oracle 8i Enterprise Server - 8.1.7 or higher
> Required LDAP: OpenLDAP 2.0.1; iPlanet 4.16, 5.1
> 
> No Linux platform.
> 
> AOL/Netscape offers a solutions as well.
> 
> http://enterprise.netscape.com/products/commsvcs/calendar.html
> 
> Again, the problem:
> 
> What operating systems does Netscape Calendar Server 6.0 support?
> 
> Netscape Calendar Server supports Solaris 8.
> 
> Now, Solaris is Unix, but I'd prefer a linux solution.
> 
> 
> 
> 
>