People asking "Is it fun" are missing the point.
Don't 'fun' yourself into a job under terms you didn't get to negotiate, state your requirements and adjust your work funnel accordingly. I've witnessed a lot of 'fun' projects manifest themselves into serious projects that fall apart because this forethought was neglected.
Well, considering this is a fun project being worked on by volunteers (some of whom are sponsored by the community), I'm going to go out on a limb and say the answer to this question will always be "zero".
(edit: based on other comments, it sounds like donations rather than streaming revenue are the major source of income, although I bet the goodwill from having such an open development process help with the donations).
Are they? I thought the whole point of the entire project was fun.