Complex sentence: From 2005 the Conferences have also served as the Meetings of Parties (MOP) of the Kyoto Protocol; also parties to the Convention that are not parties to the Protocol can participate in Protocol-related meetings as observers.
Split into simpler sentences: From 2005 the Conferences have also served as the Meetings of Parties of the Kyoto Protocol (MOP). Also parties to the Convention that are not parties to the Protocol can participate in Protocol-related meetings as observers.