Complex sentence: The site is one of the two oldest and largest "Civilization"-related community sites (the other being CFC), and has frequent interaction with their games'related developers, with postings to the groups themselves or in mentions on the developers' sites.
Split into simpler sentences: The site is one of the two oldest and largest "Civilization"-related community sites (the other being CFC). It has frequent interaction with their games'related developers, with postings to the groups themselves or in mentions on the developers' sites.