In my own personal opinion any program that receive funds from an investors and offer them higher returns in a short period is a ponzi but this program is in a beta but takes in payment and tends to doubled it.
Whether the investment is safe or real is a secondary question.
This is not a Ponzi because no coins will be returned at all. This is a reading comprehension and bitcoin network lesson
With zero transaction confirmations doesn't it mean that even his 4 BTC investment would be stuck for some time.
I normally don't invest in such sort of tricks unless I am absolutely certain that I would get my base investment back. Same is the case over here haven't put my money yet...unless the doubts are clear
Can't really understand what exactly is going on over here
It's very simple.
People that lack reading comprehension and/or knowledge of how the bitcoin network works send bitcoins to amaclin.
He does what he says he will do, and sends back "a transaction" with double the amount back immediately.
Because amaclin knows how the bitcoin network works, he will send back a transaction that will never confirm, so the only one to ever get coins will be him, because the coins he sends out will never actually get to their destination.
It isn't a ponzi scheme, because that is when old investors are paid with money from new investors. Since no one will ever get paid (except the OP) it's not a ponzi.