DECS writes: Apple is leveraging the power of open source development in a new effort to directly target Microsoft Exchange Server. The new standards based, open source Calendar Server will debut this year with Leopard Server; the source itself is already available at MacOSForge.org under the Apache 2.0 license. Rather than trying to copy Microsoft's tools, Apple is building its own vision of collaborative workgroup services. Why Apple is offering a calendar server might come as a surprise. Apple's Open Calendar Server vs Exchange Server puts Apple's efforts in the context of existing collaboration software, from IBM's Lotus Notes, to Novell's GroupWise, Microsoft's Exchange, MeetingMaker and others.