I thought the core plan was supposed to be somewhat of a low carb plan. If so, how is it that you can have popcorn- as much as you want like any other core plan (within reason, I know). But popcorn is definitely a carb so why is it okay?

Not sure since I'm not doing the Core plan but I will try to find out for you.

Anyone else have any input on this?

Whoops! I just noticed someone answered your question on the Core Board

Core is not a 'low carb' diet but it is a lower processed carb lifestyle. It teaches you to eat the better carbs and not rely so much on the refined/processed carbs. I did not look to see what they said on the carb board but I hope this helps.