Dear moderators/admins, may I please send a few members here private messages asking them if they want to join my forum? It's not like I'd spam people about it, I'll just ask them if they're interested, and if they are, then they can join and post, if not, that's okay too. It's not related to money or "rewards" or scams or anything like that, it's just a forum, similar to this one. So, may I please have your permission to send people private messages? Also, may I please post a topic about my message board on your forum?
Sure, you may feel free to do all of that.
Just don't lead anyone to potentially harmful pages (with virus and chain pop ups or stuff like that) and don't get stalkerish with the PMs (like don't go "Hey why didn't you reply to me!!" if they don't).
Otherwise I'd say there's no harm in it.