Is the registration for SG closed?

Yes, and probably not.

Registration will reopen some time after a minor site revision that cg is working on, from what I understand, it involves putting more power into moderator hands and perhaps even making it possible for moderators to see who invited whom in order to bring down repercussions on those who invite trouble makers.

Once the improved moderation tools and minor site layout tweak are completed, cg will no doubt have the increased ads in order to try and have the advertising pay for the server`s upkeep and rather high bandwidth usage fees.