I have looked at that plugin. The last couple of post seem to show that it will bring up the group but not allow people to join with out hitting the join button. I also believe that person would have to already be logged into the steam group website to use the join button. If you know another way of doing it in that plugin that will send them the invite or allow them to join let me know. As I read things and I could be wrong it is not possible at this time to have them join the group or get an invite with out those preset conditions