We are working on a major rewrite of the Felix tool, Felix architecture was quite chaotic and mostly hard to expand, so we created Flux.
Flux is a redesigned Felix. It is written in C++ and with a modular design. Still it is missing most of the features of felix and is only usable as a repeater over the UDP transport, so using felix is still necessary for live streaming and production environments, but we hope to be able to prefer Flux over Felix soon.
Flux sources are available on the usual git repository for testing, please remember the Flux is still experimental and under heavy development. So use Felix instead. Flux is available only for development purpose.