Hello Michael,
The license works as a subscription, so after purchase you get 1 year of updates. After that period, you will get an email with an offer to renew and get 1 year more of updates, if you don't renew you can still using the library, no problem here.
The only dependencies are the indy package which comes with Delphi. The Enterprise edition comes with a custom indy version so if you already have an indy version, both versions can coexist.
The discounts for renewals are: 50% for Standard, 60% for Professional and 70% for Enterprise.
Kind Regards,
Sergio