How to deploy Juju services Programmatically . Is there any API available to do the same?
Yes there is a websocket-based Juju API. You can use it from Go directly (see http://godoc.org/launchpad.net/juju-core/state/api), or you can use Juju Deployer Python wrapper around the API. It supports stack-like simple and complex scripted deployments.
The best way will be to get the source locally with