While this plugin supports multiple forms, only one can be included on a page/post. It would appear that there is no logic to control the register and unregister to/from a specific list. Placing multiple forms on the same page/post causes all list to be updated with a single button click. I have added code to fix this as well as some simple formatting issues, however the other issue exists. This would be a great plugin if these issues could be addressed by the author.