While the improvements to Mac OS X Leopard desktop are said to be evolutionary rather than revolutionary, the enhancements to Apple’s Mac OS X 10.5 Leopard Server are impressive and include features ordinarily reserved for large enterprises.

Leopard Server, which is expected to ship Friday, is the networking component of Mac OS X Leopard. It uses a 64-bit Unix kernel and ships with a new version of Open Directory, which supports Lightweight Directory Access Protocol proxy services, authorization across domains and RADIUS authentication, among other features.

Leopard Server uses the same kernel as Mac OS X Leopard desktop. Because it is 64-bit enabled it has access to the same amounts of memory as Intel 64-bit processors.

Leopard can also be integrated with Microsoft’s Active Directory and includes clustering, e-mail and calendaring servers.

The calendar server, which is licensed on a per server basis, has been aptly called Darwin – it lets users share their calendars with other users across the organization. Calendars are stored in a central location and synchronized between user desktops. The Darwin Calendar Server uses the CalDAV protocol, which allows access to calendar events via WebDAV, and thus supports Microsoft Outlook and Leopard’s iCal. It also includes a Podcast Producer, which allows the encoding, publishing and distribution of podcasts, and a Wiki server, which allows users to collaborate with other users and build and edit wiki pages.

For developers, Leopard Servers also supports the Web application framework Ruby of Rails and ships with Mongrel, a lightweight HTTP library and Web server.

The Leopard Server is also expected to ship with a new wizard called the Server Assistant, which simplifies configuration and setup. A new Server Preferences program makes it easy to create users and groups, configure firewalls and monitor utilization.

From a storage standpoint, Leopard supports the Unix/Linux Network File System and clustering with the Apple Xsan array.

Mac OS X Server version 10.5 Leopard is $499 for a 10-client license and $999 for an unlimited client edition. It is included with Apple’s Xserve server at no additional charge.