Harold (Hal) Abelson
Professor of Computer Science and Engineering at the MassachusettsInstituteOfTechnology.
Founding director of the FreeSoftwareFoundation. Member of the board of directors of CreativeCommons.
Author of the books StructureAndInterpretationOfComputerPrograms (with GeraldSussman and Julie Sussman), "TurtleGeometry: The Computer as a Medium for Exploring Mathematics" (with AndreaDiSessa), and LogoForTheMacintosh (with AmandaAbelson, see LogoLanguage).
Home page at http://swiss.csail.mit.edu/users/hal/