Absolutely you can. The base game plays 2-6 players. But with another copy, you can make the game go all the way up to 12 players. The only slow down is that players may have to wait a bit longer for a round to end if they are eliminated early from drinking something "That's Not Lemonade."
Great news your awesomeness! This campaign, we will be using a pledge manager. That means that once the campaign ends, regardless of what level you back, you will be able to add products on to your order. So if you just wanted to add a copy of Necroboomicon onto your order...no problem. Can't get enough of WCRR in your area, you can add on 12 hundred copies to your order of That's Not Lemonade. Enjoy remaining being the coolest kid in your town!
Don't see the answer to your question? Ask the project creator directly.