Easel Pro will not restrict the number of machines used with your account. There is also no restriction on how many computers can access one Easel Pro account.
However, the Easel driver cannot drive two machines at once. If you have multiple machines, they will each need a dedicated laptop or simply not run at the same time.
If you have two or more machine types, simply select the correct one from the Machine tab in Easel prior to carving.