The main development is happening on our GitHub page. Users are encouraged to contribute to the development with testing and patches. The wiki is also the product of a community effort, please go ahead and extend it if you have something useful to add to it.
The color schemes are also all user contributed, new ones can be submitted to the GitHub repository.
You can follow discussions and development on Sup as well as ask for help on our mailing list supmua@googlegroups.com.
To subscribe, send an email to supmua+subscribe@googlegroups.com. You can also subscribe on the web at https://groups.google.com/d/forum/supmua.
You can browse and search the mailing list archives on our public-inbox instance.
We used to have three mailing lists: sup-talk, sup-devel, and sup-announce. With the shutdown of Rubyforge these mailing lists were closed.