Social Entrepreneurship seems a clumsy word, doesn't it. Deriving from the French word meaning to undertake, it may have become it's own undertaker.
The original concept is attributable to Bill Drayton whose Ashoka foundation had driven many of the early efforts to apply business methods to address social problems.
Others like Skoll have followed. In all cases, supported by a nonprofit foundation which may provide start up funding, or a stipend to ensure that the entrepreneurs themselves are at least sustainable.