See Ambari Development guide on how to check out the source and build it.
You can follow all the work going on by watching the Ambari JIRA project. You can see the JIRA details for Ambari here:
https://issues.apache.org/jira/issues/?jql=project%20%3D%20AMBARI
Take a look at how to install a Hadoop cluster using Ambari 2.5.1.
Subscribe to the Ambari mailing lists and check back here often to learn about our upcoming releases.