Being a user is completely free, but there is the option of buying AFG+ that gives the following powers:
- No ads on AG, although there are certain in-game ads that AFG+ doesn't block
- Full screen and a "turn off the lights" option in games.
- Access to betas for certain games 1 week before the public release.
- Access to a forum for AFG+ members only.
Edit: It now appears that the post you were referring to is a joke.