The refusal to open-license Minix is another one that has had major repercussions.

Yes, that was a giant mistake. But you have to keep in mind that there was already a deal with Prentice-Hall at that point and re-negotiating that to open sourcing it may well have been prohibitively costly for Tanenbaum / VU.

I don't even really think it was a mistake, it's just that it indirectly caused linux. Of course the Hurd being a Turd helped there, too.

It's the Butterfly Effect, for sure.