Oh, so NOW I find this thread! Haha! I was actually looking for advice on liquid smoke this afternoon, but I didn't find it then, and I went ahead and made a 1-gallon gouda with liquid smoke. I put in a lot more than 2 tablespoons to 4 gallons. I put about 1/4 cup for one gallon, but I tasted the curd before it went into the mold and it tasted very good to me. I used the hickory smoke from Colgin. I put a couple tablespoons in after the second wash, that is, the second time I added hot water, and then again after I drained off the final whey just before putting the curd in the mold. (I used Ricki Carroll's "Home Cheese Making" recipe.)
Maybe the curd only takes so much of the liquid smoke? I don't know. The why tastes good, too. Then again, I like strong flavors.