Why can't you start the project first and then ask for donations later? Are you saying that unless you guys get paid you're not going to work on the project?
"hey I can get this for free, and I can get this TODAY. hm those developers are cool. maybe I'll donate some day"
Then they download and use the thing. 97% forget about donating and never return. Of the remaining people, they donate maybe $100 or something.
Up until recently Passenger was completely free, with donation options. Now they have an Enterprise offering - which we are happily paying for. I suspect the Enterprise licenses are orders of magnitude more than the donations ever were.
We're experimenting with a model that allows us to work full-time on a project for long enough to make it a viable production system.