When is some of it going to get spent on upgrading the forum? Seriously - the forum has collected over USD 300,000 so far.
Software developers are apparently terrible at marketing themselves. In the past 6 months I've gotten only 2-3 inquiries about the project. It's true that I'm not very good at managing this process (due to lack of time and also lack of experience with this kind of thing), but you'd think that someone would be able to find some way of getting me to hire them when there's 5000+ BTC on the line. I don't really have time to search out people for this job, and I won't convert large amounts of the forum's BTC into fiat for hiring people in more traditional ways.
My current plan is to create the core of the software (database, core API, security) myself and set bounties on sections of the rest (UI, full API, etc.). I've made some progress, but I don't have much time and my current priority is fixing some problems with SMF. Maybe I could hire someone to write this stuff under my close direction.
I've thought a lot about just using some existing forum software, especially SMF. I've become far more familiar with SMF than I ever wanted to be; it wouldn't be very difficult for me to add all of my desired features to SMF at this point. But then I think about SMF's horrible escaping mess which is guaranteed to cause security problems in the future...
All of the other forum software packages I've investigated have major problems which are IMO probably worse than just creating software from scratch, especially when we easily have the money.