If you've previously purchased Publish you can access the upgrades here
http://www.engagemodules.com/BuyNow/Upgrades.aspx
This page should allow you to upgrade between the versions, as well as renew the subscription if you're close to the end of your year.
As for the Professional license, currently that does mean multiple portals on the same server, or multiple servers, if they are all related to your organization. If you're building sites for client websites they would each need their own license.