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: 
Use [Google Calendar + CalDav](http://www.google.com/support/calendar/bin/answer.py?hl=en&answer=99358#ical).

We use it as our calendar for our business, and it's solid. iCal integration is not 100% (no tasks, each calendar is a new account), but the most important parts are even better than iCal Server IMO. Having google email or SMS you a few hours before a meeting is especially nice.
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.