It can easily be vegan if you want to make it that way. Be sure to check your chocolate bar for added dairy and the type of sugar used to sweeten it.  Most dark chocolate bars don’t have dairy added, but if you are using milk chocolate or white chocolate these often do. Also, some sugar isn’t considered vegan because they are bleached using bone char so if you want to make vegan chocolate popcorn, choose a chocolate bar that’s labeled vegan.