This "update subscription" is a per Company subscription.

So, on how many H-Sphere clusters can I install these packages now?

Simply, on any cluster that belongs to your company.
So, if you for example are using one cluster for your end-users, one for your resellers and one for Developement, you only need ONE subscription.

 What if you are a System Administrator working for multiple companies?
You need to purchase one license per company BUT, contact us first we might just have a very interesting offer for you!

The same is true if you have multiple companies that you would like to resell to, let us know we will have a sweet deal waiting for you.