How to license Xamarin on a build server?

We want to use Jenkins to setup automated builds for Continuous Integration.

This page suggests that it possible http://docs.xamarin.com/guides/android/advanced_topics/build_process/#22-build-targets

We have "Business Edition" accounts.

1) Do we have to purchase another license just for the build server? 2) As this is a "headless build" we do not want to install any IDEs so how do we get the license onto the build server?

(Initially we will be doing this for an Android build and the build server will be Windows)

Thank you