Platform: OS X Server
Mac App Store availability confirmed by Apple; requires the underlying OS.
Apple source ↗Apple's October 22, 2013 announcement made Mavericks free but kept OS X Server 3.0 at US $19.99 on the Mac App Store, requiring Mavericks. The free client must not be confused with a free server add-on. Although the URL contains October 23, the release's displayed date and text are October 22.

Apple · Server 3.0 / Mavericks · 2013-10-22
Apple's October 2013 overview highlights Xcode Server for continuous integration, testing and repositories; Profile Manager for configuring devices and distributing institution-licensed apps and books; and Caching Server for Apple-distributed content. This expanded the server's role in development teams and Mac/iOS fleets. The guide requires a Mac running Mavericks and 10 GB free, with extra space for some features.
Apple · OS X Server · October 2013 · pp. 4, 29
Writing in Macworld on October 23, Serenity Caldwell explained that Server still cost money and cited SMB2, Profile Manager and Xcode Server improvements. This is contemporary news, not a comparative performance test. Apple's overview confirms the features; Caching Server is not presented as a Mavericks-only invention, since it was already documented in updates to the previous generation.
Andrew Cunningham · Ars Technica · 2013-01-16 · Apple · OS X Server · October 2013 · pp. 4, 29 · Serenity Caldwell · Macworld · 2013-10-23
Server 3.0 is the application version, while Mavericks is OS X 10.9. This entry does not call the add-on OS X 3.0 or turn a modern support-document edit date into a historical launch date. Prices, services and requirements are preserved as information about the 2013 product, not advice to install old software today.
Andrew Cunningham · Ars Technica · 2013-01-16 · Apple · Server 3.0 / Mavericks · 2013-10-22
Selected releases, not a complete history. Dates follow Apple's release records, not the latest page edit. No builds are included.
ISO date: year-month-day.
Platform: OS X Server
Mac App Store availability confirmed by Apple; requires the underlying OS.
Apple source ↗