As a short answer no you can not run two servers on the same license at the same time (unless a cluster license of course). Generally one of these servers will kick the other one offline or off duty. This might not happen straight away but a soon as they "find" each other on the network this will happen. You can of course install the server and not enter the license or if you have a service window you can have two servers with the same license as long as only one QlikView server service is running at the same time. This is used as a backup solution where you have a "hot/Cold" setup, if one server goes down you can fire up the second.
Thanks for the response.
In the documentation "QlikView 11 Upgrade & Migrations Section 5: Re-locating QlikView Services, Step 2: Migrate settings" I need to copy the following three files:
Lef.txt - License Enabler File I think? Can I skip this step and continue configuring the new server while having the current live server running? Then once we're ready to switch over, move the Lef.txt file?
I presume you may have done your server migrate by now, but for others finding this thread;
You can not use the same licence on two servers at the same time. The servers send out messages and when two are found with the same licence key one will shut down (and perhaps not the one you want).
Qlik provide a 30 day migration licence key for licenced users to upgrade from one server to another whilst allowing a period of parallel running. You are entitled to one of these migration licences for free in every calendar year.
Hope that helps,