Hello Eric M., By default a link such as <a href="https://app.roll20.net/campaigns/details/1234567/s" rel="nofollow">https://app.roll20.net/campaigns/details/1234567/s</a> ... is only visible to players already in the game, and only Plus and Pro subscribers can make their games visible to the public , but even then people not in the game can not post to the forums. The best way to handle this situation is to create a Looking for Group listing ; even if you do not enable it for viewing in the LFG Directory you can share the link with others and have a separate Listing Discussion forum just for those potentially interested in your game. As a bonus, anyone who posts to your game's Listing Discussion forum will have a big blue button by their username and all a GM has to is click 'Invite to Game' and an invitation will be sent their way. I hope this helps, happy gaming! :)
