Question: I have to sync iCal on all the computers without having a MobileMe account, I would like it to be "live" because the co-workers have to see the changes right away on their screens, they also need to be able to edit and stay sync on the rest of the LAN.

There isn't a server available - so a server solution such as iCal Server won't work.

Answer: 
One option would be to use [iCal server](http://www.apple.com/server/macosx/features/ical-server.html) which is apart of Mac OS X Server.

Or

Publish iCal calendars with local WebDAV server.
I up-voted for Google Calendar + CalDAV as I use that for my personal calendars and it works well for me, but I don't use To Dos/Tasks at all so I don't miss that functionality.

I wouldn't suggest using Mac OS X Server's iCal Server (also CalDAV-powered) anyway as there are still a few odd bugs w/group calendars, permissions, re-sycing when disconnected, etc. Also, it really requires an Open Directory setup with the workstations bound and don't expect to be able to invite anyone to meetings if they aren't in Open Directory. Overall it's okay, but probably more work than you're looking for.

One other suggestion is [BusyMac's BusySync](http://www.busymac.com/busysync/index.html). Shareware and does a great job of sharing & syncing calendars on a local network.