You can install it on un-limitted of your OWN sites. However, if you want to use it for a client, then you will need to purchase a new license for each new clients. Is my answer clear ?
Just to be shure, based on the answer you gave to MikeWelsh, what if my client has 2 websites? One is for a organization and the other is for a conference the organization put togehter yearly but the domains are diferent.
