well linux was originally based on minix, but of course needed to have all minix code replaced with new code for it to be released under a new licence (the GPL).
interestingly that tree shows minix being based on unix v8? i find that hard to swallow since minix is an open source teaching tool. perhaps the CLI is based on it, but surely none of the code is?
systems such as GNU, BSD and linux are all based on unix in that they all began as unix, and their developers rewrote the entire system bit by bit until none of the original unix was left, this is why fanatics bite your head off, there is no unix in linux. still, it's look and feel is based on unix, and by the looks of things, it's true to say unix is an ancestor to linux too.
