How many posts must we have in the newbie section to be able to post on other forums?

5 posts and 4 hours online it is

Thanks, I saw somewhere that it requires only 1 post & 4hours online.

Well, that's correct, as the newbie sticky clearly states that you have to post once and then wait 4 hours.

https://bitcointalk.org/index.php?topic=177133.0