With OS X 10.11 "El Capitan" set to hit Macs on September 30, Apple has updated the OS X Server app to version 5.0, and it's a free upgrade for users of the year-old Yosemite operating system.
"OS X Server 5.0 is now operating system version independent. The same version of Server can be used on Mac computers running OS X Yosemite 10.10.5 and OS X El Capitan 10.11," Apple notes.
This change is a break from Apple's past policy. Although the desktop version of OS X is free (if you've bought a Mac, that is), the server app costs $19.99 and until this year had to be re-purchased for another $19.99 with each new OS release. Now, though, the $19.99 server bundle will work on multiple versions of OS X.