You can have a single TubeBuddy account with multiple channels registered to it, but each channel will need their own, individual licenses. You can add a channel by going to tubebuddy.com/account and hitting the green 'Add Channel' button in order to register additional channels onto your account. But if you would like for them to have paid licenses they will each need their own.
On that note, we do offer a 50% discount off the purchase of a second license. You just need to use the discount code RepeatBuddy at checkout.