This add-on cannot be used independently. It needs to be installed if you need Excel exports in Requirement Yogi or Play SQL Spreadsheets.
The reason why it's provided separately is to share the library. It weighs 15Mb and there's no reason to have one instance in the JVM for each add-on that needs it. For example, it is already included twice in Confluence, in the Document Conversion Library and in the Office Connector plugin.
It is open-source and it relies on Apache POI. Please see https://poi.apache.org/legal.html for legal and copyright information.
Please see https://bitbucket.org/aragot/play-sql-exports for the source.