The program lies within Education Tools, more precisely Reference. This free Mac application is an intellectual property of John Wells.
From the developer:
Ringo is a smart WaniKani companion for OS X. Ringo lives in your menubar, making it easy to complete your reviews and lessons right on the spot. Through integration with OS X notifications, Ringo informs you of new lessons and reviews as they become available.
You may want to check out more Mac applications, such as USA-Manual-Mac, Bible Sander or Biology, which might be related to Ringo.