For those who have not participated in a hackathon before, the broad idea is to get people from a wide variety of experience and backgrounds together to solve problems over a short period of time - typically 24 or 48 hours. Details vary, but typically at the start of the event, people pitch ideas and groups form organically based on what people are interested in. The groups then work together intensively, often fueled by pizza and caffeine etc. At the end of the hackathon the groups present their work and there are often prizes for the best hacks.
The general idea of virtual FSWeekend hackathons is to encourage existing and new contributors to collaborate over the course of a weekend to create new and exciting features for FlightGear in the broadest sense. The core developers would particularly like to use it as an opportunity to encourage people to get their hands dirty in the core code, so they will be primarily there to help/coach people rather than hacking themselves, but anything is possible :)
No prior development experience is necessary - there might be run some education sessions ahead of the weekend so people can hit the ground running (otherwise you will learn during the hackathon). Also, do not feel you have to commit to coding the entire weekend to the exclusion of all else. We think participants will still get real value if they can just commit to one day and some late evenings.