If my team don't work on a project made by unity, do I have to pay for their license?

I actually want to use unity for a game and only I will develop and update the game in the future. If I add someone, I will surely pay for them. But I think my friends are going to join to me also in the same studio and they are working on other engines. If in future only I work on the game I made with unity and let's say our team member is 5. Now, do I have to buy the license for 5 people, or do I have to buy it for me only [As I'm the only one going to use unity in the project and I'm the only one going to work on that project.]