License Question Multiple Site License ??

Hello I am testing out the free media folders just loving it so far works better then the the other I have used in the past .
Thinking of going pro do you have mutisite licensing???? ..
license for multiple sites… or domains ..I have 3 blogs on two domains .

One domain has two blogs ( they are installed as a mutisite layout ) They are tied together .

Other Domain has one blog .

Would one license cover for both blogs on one domain..I understand two license for two different domains .. was not sure of the two blogs tied together on one domain .

I only need a 3 site license . Thanks