License related Question

Hi,

We are planning to use Vault as our KMS in one of the solutions we are building as part of company. We would like to understand the licensing aspects of vault. We are using vault as one of our components. We are deploying planning to deploy valut in EKS cluster for customers. Do we need to pay any license? we are not going to modify any vault code neither we are going to provide vault alone as managed service. If someone can clarify it will be very helpful for us to choose a KMS for our solution.