For those that were not part op Skype for Business Server 2015 TAP program, the UCMA 5.0 SDK version 9319.48 is now also public available on Microsoft Download Center at UCMA 5.0 SDK and runtime languages version 11.
The installation documentation is somewhat limited. If you install UcmaSdkSetup.exe followed by following the instructions described in the documentation
"C:\Program Files\Skype for Business Server 2015\Deployment>Bootstrapper.exe /BootstrapLocalMgmt /MinCache"
you will probably will encounter
"Error encountered: Error returned while installing OcsCore.msi(Feature_LocalMgmtStore), code 1638. Error Message: Another version of this product is already installed"