SongKong 5.3 is the latest release - available from 26th of April 2018
SongKong is available for OSX, Windows and Linux.
Without a license SongKong runs in Lite mode.
The Metadata Status Report and Manual Metadata Editing are both fully functional in Lite mode and can be controlled directly with the Desktop application or via a web browser using the Remote User Interface
Automated Matching and Duplicate Deletion can be run on many songs as you like in preview mode, you can see exactly what changes would be made but no changes are actually saved to your songs without purchasing a full license.
To convert from Lite to a full installation you just have to purchase the correct license and enter the license details.
Detailed installation instructions are available from here