It says everyone is invited, so I'd assume it's not just for VU students.
The Aula at the VU is pretty big and I hope there will be enough space for everybody, but regardless they won't complain if non-students join as well (at least I assume so).
I really wanted to attend as well, but unfortunately I will be away from the country in those dates, you can take "my place" if you want :P
The Aula at the VU Amsterdam has 900 seats. With this kind of announcement (and showing up at HN) I guess the seats will be filled quickly. Registration is free, and it is polite and appreciated so the organizers know how many people they can expect, but registration is not required. Anyhow, if you want to attend the farewell lecture: show up early :-)
And it would not surprise me if they relocate the lecture to a bigger auditorium nearby, if interest or registration goes way beyond 900.
