Openfire Scalability to manage 1000000 concurrent users

I am working with Openfire server. I want to manage 1000,000 concurrent users. I found that there are two ways to make Openfire scalable i.e.

1. Through Clustering Openfire.
2. Through Connection Managers.

I need information about the following queries

• Is there any licensing cost for clustering Openfire v3.9.1 commercially.If so, how much that cost is.
• How many application nodes are required for setting up cluster to manage the desired number of concurrent users. 
• I also read that the Coherence-based clustering plugin has been deprecated, so which plugin will be used to setup a cluster of Openfire v3.9.1.
• Is there any licensing cost for scaling it with Connection Managers.
• How many Connection Managers are required to manage desired number of concurrent users.