As senior attorney with the National Resources Defense Council, chief prosecuting attorney for the Hudson Riverkeeper and president of the Waterkeeper Alliance, Robert F. Kennedy Jr. has filed more than 400 lawsuits against alleged polluters and even gone to jail for the environmental cause.

So when the Kennedy scion became a partner of VantagePoint Venture Partners, a venture capital firm that invests in “clean technology,” earlier this year, it was another sign that “green” is coming of age commercially. The Silicon Valley–based firm, which also targets information technology, health care and Asia, has invested about 22 percent of its $4.5 billion in committed capital in such clean-tech enterprises as generators of solar and wind power.