Actually, I made it to be used as role or stand-alone playbook, so you can use it easily (You can also use this lovely script "ansible-role-apply" to run any role directly).
To use it directly:
ansible-playbook ansible-latest-s3cmd.yml
To use it as role in a playbook:
- name: Ansible role to install and configure latest version of s3cmd (via pip).
  hosts: s3cmd-servers
  sudo: true
  gather_facts: no
  roles:
    - ansible-latest-s3cmd
Variables:
s3cmd: - key: 'AWS_KEY' - secret: 'AWS_SECRET'
And if you are a security freak like me, you should take a look at Ansible "Vault", which allows keeping sensitive data such as passwords or keys in encrypted files.
That's it :D