The source for the client is here: https://github.com/letsencrypt/letsencrypt https://github.com/letsencrypt/letsencrypt However, their release schedule dictat

The source for the client is here: https://github.com/letsencrypt/letsencrypt https://github.com/letsencrypt/letsencrypt However, their release schedule dictates when the service (yes, the client is part of this) is ready for use. Until then you are waiting for the service to be available.