Best of class Sentiment analysis on Twitter and social media
Umigon is free to use and works on social media texts in English or French. Initially released in 2012, it is still under continuous development (closed source). It is available in "Nocode functions", a web app offering other free functions for text and network analysis.
Read the original paper here.
The code base has moved to new repositories -> there. The repo you are visiting here is archived.