As far as I understand all of the library/business logic is actually implemented in java and available in its own repo (linked in the readme). They then wanted

As far as I understand all of the library/business logic is actually implemented in java and available in its own repo (linked in the readme). They then wanted a client application but didn't want to build a GUI in java (I assume?) so they grabbed ruby and created a webapp? That said, it seems like you can run a CLI version using only java and nothing else.