There is no stable release. This is unsupported, pre-alpha software: use at your own risk!
The sources for FV3Config can be downloaded from the Github repo.
You can clone the public repository:
$ git clone git://github.com/VulcanClimateModeling/fv3config
Once you have a copy of the source, you can install it interactively with:
$ pip install -e .
The -e flag will set up the directory so that python uses the local folder including any modifications, instead of copying the sources to an installation directory. This is very useful for development.