> Mac OS X Server 1.0, released on March 16, 1999, is the first
> operating system released into the retail market by Apple Computer
> based on their acquisition of NeXT. It followed the Rhapsody series
> of developer releases of what was to be known as Mac OS X. Although
> OS X Server 1.0 had a variation of the Platinum "look and feel" from
> Mac OS 8, it is based on the OPENSTEP (and thus, NeXTSTEP) operating
> system instead of the classic Mac OS, giving users a preview of the
> future operating system Mac OS X. It was replaced by a version based
> on Mac OS X v10.0 in 2001. (Source: [Wikipedia][1])

See also: [Mac OS X Server 10.0][2], [Mac OS X Server 10.1][3], [Mac
OS X Server 10.2][4], [Mac OS X Server 10.3][5], [Mac OS X Server
10.4][6], [Mac OS X Server 10.5][7], [Mac OS X Server 10.6][8]

Compatibility
Architecture: PPC

Officially, it runs on some PowerPC G3 & G4 Macs
A list of supported computers is here: [http://support.apple.com/kb/TA28250][9] (Wayback Machine link).

  [1]: http://en.wikipedia.org/wiki/Mac_OS_X_Server_1.0
  [2]: http://macintoshgarden.org/apps/mac-os-x-server-100-691-3209691-3046
  [3]: http://macintoshgarden.org/apps/mac-os-x-server-101
  [4]: http://macintoshgarden.org/apps/mac-os-x-server-102
  [5]: http://macintoshgarden.org/apps/mac-os-x-server-103-unlimited-clients-edition
  [6]: http://macintoshgarden.org/apps/mac-os-server-104
  [7]: http://macintoshgarden.org/apps/mac-os-x-server-105
  [8]: http://macintoshgarden.org/apps/mac-os-x-server-106
  [9]: https://web.archive.org/web/20090603172159/http://support.apple.com/kb/TA28250