It doesn't appear to be that difficult to become a domain reseller. Here's the service provided by Key-Systems that Coffee & Domains is using: https://www.rrpproxy.net/website/domains/reseller/

No, there's a difference. Wikipedia's "Reseller" article explains it better than I can:

"Resellers are known to conduct operations on the Internet through sites on the web. For example, this occurs where individuals or companies act as agents for ICANN accredited registrars. They either sell on commission or for profit and in most cases, but not all, the purchase from the registrar and the sale to the ultimate buyer occurs in real time. These resellers are not to be confused with speculators, who purchase many domain names with the intention of holding them and selling them at some future time at a profit. Resellers, by the very nature of their business are retailers."