Could you do a stuck FAQ about licensing ? not just upgrading licenses ? I have found many messages about licensing, but not any answering my question below

I'm in the process of evaluating Veeam Backup and Recovery.
I have two ESXi hosts. One is production, the second one is backup. So far, nothing special. If I got it right, I just need licenses for each sockets on the production host.
However... If I failover a vm, use it for some days, and want then to make a replica back to the production host, to "fail it back", then, my backup server becomes a source... Therefore, I would have to buy licenses for this one too... Am I correct ?
If I am, then, what would be the way to make a "failback" without buying additional licenses, knowing that this is the only situation where my backup server will be a source... The planned "easy fail back" feature will solve this issue. But for now ... ? how to proceed ?