What do you find complicated?
I didn't want to start a discussion with Ditto, but imho he's partly still looking at it the wrong way. Reseller+selling lifetime license wasn't directly illegal, it depends on the situation.
The way of speaking can cause complications. People also talk about reselling when datacenters or vps/dedi hosters "sell" internal licenses to their custumers, which can only be "sold" together with a vps or dedi server.
Reselling internal licenses was allowed before too. Ditto made it a bit complicated. We have a lifetime internal license. However, we can only use that at a certain datacenter. Since we don't have a server there anymore, that license can't be used until we do again. The datacenter is called the reseller.
So yes, also in the past a reseller could sell legally lifetime licenses.
There were also people (hosters/resellers) who were buying and reselling the "normal" lifetime licenses, he wants to call it used licenses, but that doesn't matter, used or not used, they are/were lifetime licenses. And there were company's trading them which was also legal at that time. However, this is not a "official reseller" as some other panels have/had. They never existed as far as I know.
I don't know how it works with selling lifetime internal licenses, only to be used in the datacentrum you bought them. I don't know if they still exist or nowadays only renting of internal licenses from datacenters are possible.