Hello,
Yes, the Content Staging target should be set to only one of the servers in the Webfarm,
since the inter-server synchronization is then performed by Webfarm synchronization module itself.
When you run Kentico
CMS on several servers in the web farm, you need to purchase a license for each server in the web farm. This applies also to the 1 Web Site License.
Did you have any specific questions about the web farm server licensing?
Best Regards,
Edward Hillard