Hi

With MEP 17 and 2013 one license covers one install on a computer - so for 2 computers you need 2 licences.

MEP 2015 has a different licencing system - you can install the software on as many computers as you require, however you can only activate on one computer at a time. 

You can transfer the activation to another computer once per month.  If you want to use more than one computer in a month then you need a license for each computer.

HTH

John EB