Hey there,
Great question, let me clarify it for you.
With Galileo FX you can trade on 1 LIVE ACCOUNT and up TO 5 DEMO ACCOUNTS at the same time.
So if on MT4 your account is Live and on MT5 your account is DEMO yes you can trade with Galileo FX at the same time.
If both accounts are LIVE accounts you would need another Galileo FX license.
1 Galileo FX License = 1 LIVE ACCOUNT