With how the forums is set up, to combat spam, all new users will need post approval for every post they wish to make. However, once one post you've made is accepted, you'll be automatically moved into another group, which is free posting.
This is mainly a counter-measure we've had to implement to help combat bots and spam on this forum. Our intentions are not to filter every post anyone wises to make, but more to keep the forums cleaner. Its worth noting all posts still need to be within our rules.
The Squid Network team