I recognized quite a few, since I met several of them at the old Usenix conferences I used to attend. Dennis Ritchie, Eric Allman, Kirk McCusick, Keith Bostic. A few others. I would like to have seen the late Evi Nemeth, but she was known more for System Administration than for open source, I suppose. I also recognized Guido van Rossum and Keith Packard, again from conferences. You really get to match a name to a face at events like that.