Complex sentence: All of them are free-to-air channels, all of them are the official digital terrestrial television and DVB-T2 providers of the nation (since 2005, approved by the Korean Government).
Split into simpler sentences: All of them are free-to-air channels. Furthermore, all of them are the official digital terrestrial television and DVB-T2 providers of the nation (since 2005, approved by the Korean Government).