One who is classified as a Venkon Supporter is slightly beyond just being Neutral. A Venkon Supporter believes in what the Venkons are doing is right and they would rather see them win, not the Ivichs. A Venkon Supporter does not get involved in the war, but acts as moral support for the Venkon side.
The difference between Neutral and Venkon Supporter is the fact that someone who is completely Neutral shows no support in either side, will not get involved, but may/may not take interest in the war itself. A Venkon Supporter will not fight, but will support the Venkons in hopes of their victory.