This seems to contain a definitive answer to the question about the meaning of the logo:
https://ask.sagemath.org/question/7667/geometric-name-of-sage-logo-existence-of-dual/ -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/81a1e536-b54a-4b50-9b83-11908ceee21fn%40googlegroups.com.
