Active in DLA Piper pro bono projects, William was named Pro Bono Partner of the Year for the Washington, DC office in 2004. In 2007, the Capital Area Food Bank awarded him its Dr. Martin Luther King, Jr. Keeping the Dream Alive Award for his work in support of federal funding for the Food Bank's expanded operations. He is also a former board chairman of Habitat for Humanity of Washington, DC.

William currently serves as counsel to and on the board of directors of the National Archives Foundation, working closely with the Archivist of the United States and the Archives staff. William is also a member of the board of directors of Running Start, a DC-based non-profit which trains and inspires young women to seek political office with an aim of bringing greater equality and diversity to government.