I feel the type of leader most valued in the voluntary sector is someone who is passionate about what they do and is willing to go above and beyond their required work load. They also need to have fantastic people skills as maintaining a good work ethos for your team of volunteers who don't have the incentive of being paid is a difficult task to achieve.
These are the two most important traits in my opinion. They are definitely good traits for the company as a whole. I think the first trait could be a negative one for the leader in question though as they can be taken advantage of and their own mental health could be at risk if they take too much on.