I’m not sure if I follow the difference.
RPGnet is a professionally-run roleplaying resource with the biggest roleplaying forum on the web. They host articles, columns, reviews, a roleplaying product database, and some massive forums. Some of their forums have such a high turnover that often you don’t see any of the topics from the previous day on the first page of the forum.
I think their vision for the larp forum is to get it up to the “massive turnover” level that characterises the whole site. Given that there are no international larp forums that reach this highly stimulating level of activity, I think it’s worth supporting.
They don’t want an off-topic chatroom, if that’s what you’re wondering. Everything has to be roughly on topic, their mods are fairly strict.