Again, if anyone has any opinion on this, or first hand knowledge of Brussels, that would be welcome.
My experineces from three previous FOSDEMs: The conference closes down at 18:00 each day and then, there is not much to see in the university area. It usually was possible to find and affordable hotel in walking distance to the Grand Place, which is cool to walk around in the evenings (and makes it easy to access the Friday evening event then). There are also pubs and bars to hang out (yes, even non-touristic ones), if the hotel lacks this. So, my suggestion would be a hotel 1-2 km away from the Grand Place.
Wolfram