hello guys, "Ads after first post" is ok! I want to ask, how about ads after first topic? is this against Google TOS? Thanks for help.
No, google doesn't have TOS that specific (yet). Sure you can have adsense below the first topic in a forum. But do make sure the adsense can't be mistaken for a topic itself. That is misleading visitors and that IS against google TOS.
You should also take care not to make your Adsense ads look like posts (e.g. having a member profile such as Sponsor, Advertisement etc.)