This is only the docker image for the aws cli. This has no connection with the development of the aws cli.
For info on the cli command and options see docs.aws.amazon.com/cli/latest/userguide/cli-chap-using.html
The ENTRYPOINT for the image is the aws cli.
Without passing any commands it will run --help by default.
So docker run gruen/awscli is the same as docker run gruen/awscli --help
The /home/aws/.aws volume is set to add your credentials.
The simplest way to run would be something like the following:
docker run -it --rm \
-v "${HOME}/.aws:/home/aws/.aws" \
--name funky_fresh_name \
gruen/awscli {COMMAND} [OPTIONS]