Project Management

I am helping a friend set up his new business and he would like to be able to have a project management script hosted locally on his server. His employees are a very diverse group of people, some like using Ical and others Thunderbird. He would like a script where he can add events using Ical but still be shown on the site. As well as task projects milestones and the normal stuff. I showed him basecamp and he seemed to like that but did not like the idea of it being hosted on someone else sever. I also showed him activeCollab which he liked but that does not allow you to use stuff like ical or outlook in both directions. I was wondering if anyone knew of another script that would work for him and that would be easy enough for non computer tech people to use.