It's not unreasonable to ask for a way to recoup your development/porting costs.
It's also not unreasonable to try to abide by the wishes of the development team.
I'm guessing that the original development team already have stable jobs -- do you? is your freelancing consistent? I'd venture "not completely"
I'm also guessing that this individual developer feels that the only business model for Linux is to make free software, and screw any bottom-line business model.
This specific developer in question sounds like he got burnt by focusing on the development of xpilot at the sacrifice of his finances. While I admire his support of the community to such lengths, it's not fair to think that everyone should make the same mistakes he made.
You can do a multitude of things. The single BIGGEST thing you can do for this project is bring this back into the public eye, which you're doing now. A microtransaction of a few dollars isn't going to break anyone's bank (compare free Linux to commercial UNIX, and it's a very clear distinction). I feel that you're on the right track myself.
DO keep the source code available though. You're looking at this as under a VENDOR paradigm.