Some context: Andy Tanenbaum is born in March 1944, so already 70. That's five years after the common retirement age for his age group in The Netherlands (assuming that he paid his social taxes here).

So, in all respect a well-deserved retirement... and I guess that retired or not doesn't stop him contributing to the CS field. Well, he will have less Ph.D.-students, so more time to writing, programming and lecturing!