There are pictures at the bottom of the announcement with tables of devs working in teams, implying the whole event is in person, but the grand prize being travel to the indiecade festival makes me think otherwise.
It seems unlikely you'd expect all the participants to travel on such short notice, but I just want to be 100% sure on this before I make any concrete plans. If we are expected to travel to California (or already be in California) for 3 weeks it will make it impossible or me attend barring some miracle.
From the description, the "VR Jam" competition is a three-week game development competition with a traditional format. You're intended to form your own team and work together to create something within the three-week timeframe, which then gets judged by a jury (who the jury is is not yet specified, but it seems likely to be the same IndieCade jury that judges their own side of the event). Winners then get cash and some table space at IndieCade. It is not a "Jam" in the "Global Game Jam" sense where you get a lot of people (usually strangers) together to work on things collaboratively.
From the questions in this forum, it's clear that the "Jam" in the competition title is confusing a lot of people. Particularly since Oculus have provided photos of IndieCade's break-out rooms, which look a lot like what one would see at a Global Game Jam.
To be clear: those photos are *not* of what VR Jam will be like. The photos are of IndieCade work areas; places you'll likely see and spend time in if you attend IndieCade. I imagine that if you go to one of Oculus's "Playtest Hubs", the scene will probably be similar to what's in the photos. Although since the development time is spread over three weeks rather than a single weekend, they'll probably be rather less crowded/social.