@63352059-plesk-staff I can only assume by Mkrasikov's saying "if I prefer to separate my mail services from my main hosting" would be that the license could be applied to two servers. (spit meaning more than one)

As I mentioned, aside from Mkrasikov's reason, I have set up a test server (at home) running the same IOS as my main server and it would be beneficial to me to be able to install Plesk on the test server without having to purchase a separate license just so I could test updating something. This was true when I originally commented and is now again. ~ I want to test updating something but would need a separate license to run Plesk for longer than a 'trial period'.

My thought;
I currently use Plesk Web Pro. Why not allow me to use my Plesk Web Pro on two servers. If I can only have 30 sites, what does it matter if I have 29 sites on one server and 1 site on the test server?

I would agree, just think about the applications where this would be useful! In my case, I'm new to Plesk (and CentOS) and I want a test bed, for example; so I don't crash the live environment/server when I'm trying to update or install something. For now, I guess I have to go with a trial but that's not going to help me when I actually want to update something in the future (or give me a chance to play and explore).

Still wait for this...

I think this is a nice idea also. We have multiple plesk servers for various code bases so that each VPS can be spec'ed and tuned accordingly. The downside is that mail is all over the place.
We have started to move clients onto a central mail system but not using plesk as this type of license is not available.