BlackMageJ: If you want two copies (say, to give one as a gift), then you have to buy one of them as you can only get one freebie per account.
skeletonbow: If someone wants to have more copies of the game than the one freebie gives them (for gifts for example)
I was going to suggest that in this case you can easily create multiple accounts (it literally takes seconds; GOG doesn't even verify emails, so you can just put aghaoifutgh@aiughairutgh.asdf and be on your merry way), but...
The codes expire on the 27th of June. So if you want 2 (or more) of the never-expire codes, you have to buy Rebel Galaxy itself.
So thanks, you did indeed find a legitimate reason of using Rebel Galaxy's discount. Congrats. Of course why would anyone want multiple codes of a game that everyone and their mother will have is beyond me, but I saw someone want to trade Dragonsphere codes for The Witcher 3 right after the former was no longer free, so nothing will surprise me.
It's just sad. Someone took the time and effort to come up with a discount for this game (70%) and now this discount will cry itself to sleep because no one wants to make use of it.