Don't put too much stock in who did or did not attend the Grand Challenge. The DARPA rules state that no gov't funds can be used, either directly or indirectly, to help with the "design, development, construction or operation" of the robots or their software (Rules, p.8, Section 2.4). Delete all gov't funded robot efforts and that takes out an awful lot of research, projects, algorithms, software, etc. Just try to locate a robot research paper that doesn't refer to some gov't funded effort in its history somewhere. It's both impressive to see how far they got and depressing when most of the failure modes seen are known, fixed issues. But the fixes were done by groups working on gov't funded (in whole or in part) efforts so they're going to have to re-invent those wheels all over again...